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Compact and concise, including 
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medicine, with Pronunciation and 
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BASED ON RECENT MEDICAL 
LITERATURE. 

BY 

GEORGE M. GOULD, A.B.,M.D., 

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logical Dept.,Ger 7 nan Hospital , Phila- 
delphia. 

SEVERAL THOUSAND NEW WORDS 
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HUMAN PHYSIOLOGY. 


SIXTH EDITION. ENLAROED. 


NEW EDITIONS. 


Blakiston’s PQuiz-Compends? 

A New Series of Manuals for the Use of Students 

and Physicians. 

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4®“ These Compends are based on the most popular text-books, and the lectures of 
prominent professors, and are kept constantly revised, so that they may thoroughly repre¬ 
sent the present state of the subjects upon which they treat. 

4®* The authors have had large experience as Quiz-Masters and attaches of colleges, 
and are well acquainted with the wants of students. 

4®“ They are arranged in the most approved form, thorough and concise, containing 
over 300 illustrations, inserted wherever they could be used to advantage. 

4 ®* Can be used by students of any college. 

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No. i. HUMAN ANATOMY. Based on “Gray.” Fifth Revised and Enlarged 
Edition. Including Visceral Anatomy, formerly published separately. 117 Illustrations 
and 16 Lithographic Plates of Nerves and Arteries, with Explanatory Tables, etc. By 
Samuel O. L. Potter, m.d., Professor of the Practice of Medicine, Cooper Medical 
College, San Francisco; late A. A. Surgeon, U. S. Army. 

No. 2. PRACTICE OF MEDICINE Parti. Fourth Edition. Revised, Enlarged 
and Improved. By Dan’l E. Hughes, m.d., late Demonstrator of Clinical Medicine, 
Jefferson College, Philadelphia. 

No. 3. PRACTICE OF MEDICINE. Part II. Fourth Edition. Revised, Enlarged 
and Improved. Same author as No. 2. 

No. 4. PHYSIOLOGY. Sixth Edition, with new Illustrations and a table of Physiological 
Constants. Enlarged and Revised. By A. P. Brubaker, m.d.. Professor of Physi¬ 
ology and General Pathology in the Pennsylvania College of Dental Surgery; Demon¬ 
strator of Physiology, Jefferson Medical College, Philadelphia. 

No. 5. OBSTETRICS. Fourth Edition. Enlarged. By Henry G. Landis, m.d., 
Professor of Obstetrics and Diseases of Women and Children, Starling Medical College, 
Columbus, Ohio. Illustrated. 

No. 6. MATERIA MEDICA, THERAPEUTICS AND PRESCRIPTION 
WRITING. Fifth Revised Edition. By Samuel O. L. Potter, m.d., Professor of 
Practice, Cooper Medical College, San Francisco; late A. A. Surgeon, U. S. Army. 

No. 7. GYNAECOLOGY. A Compend of Diseases of Women. By Henry Morris, 
m.d., Demonstrator of Obstetrics, Jefferson Medical College, Philadelphia. Illus. 

No. 8. DISEASES OF THE EYE, AND REFRACTION, including Treatment 
and Surgery. By L. Webster Fox, m.d., Chief Clinical Assistant, Ophthalmological 
Department, Jefferson Medical College Hospital, and George M. Gould, m.d. With 
39 Formulae and 71 Illustrations. Second Edition. 

No. 9. SURGERY. Minor Surgery and Bandaging. Fourth Edition. Enlarged 
and Improved. By Orville Horwitz, b.s , m.d., Demonstrator of Surgery, Jefferson 
College; Chief of the Out-Patient Surgical Department, Jefferson College Hospital; 
late Resident Physician Pennsylvania Hospital, Philadelphia. With 84 Formulae and 
136 Illustrations. 

No. 10. CHEMISTRY. Inorganic and Organic. Third Edition. Including Urin¬ 
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Henry Leffmann, m.d., Professor of Chemistry in Penn’a College of Dental Surgery, 
and in the Woman’s Medical College, Phila. 

No.11. PHARMACY. Third Edition. Based upon Prof. Remington’s Text-book of 
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Woman’s Medical College, Philadelphia. Third Edition, carefully revised. 

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Surgeons; Physician to Bellevue Dispensary, and Lecturer on Genito-Urinary Surgery 
at the New York Polyclinic, etc. With 29 graphic Illustrations. Just Ready 

No. 13. WARREN. DENTAL PATHOLOGY AND DENTAL MEDICINE, 
containing all the most noteworthy points of interest to the Dental Student. By Geo. 
W. Warren, d.d.s., Clinical Chief Pennsylvania College of Dental Surgery, Phila. 
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? QUIZ-COMPENDS. ? No. 4. 


A 

C 0 M P E N D 


OF 


HUMAN PHYSIOLOGY. 


ESPECIALLY ADAPTED FOR THE USE OF 
MEDICAL STUDENTS. 


BY 

r 

ALBERT P. BRUBAKER, A.M., M. D., 

M 

DEMONSTRATOR OF PHYSIOLOGY IN THE JEFFERSON MEDICAL COLLEGE; PROFESSOR 
OF PHYSIOLOGY, PENNSYLVANIA COLLEGE OF DENTAL SURGERY ; FELLOW 
OF THE COLLEGE OF PHYSICIANS OF PHILADELPHIA. 


SIXTH EDITION, REVISED AND IMPROVED. 


WITH NEW ILLUSTRATIONS 


A TABLE OF PHYSIOLOGICAL CONSTANT 


JUL 20 1891 


ISHIN 




PHILADELPHIA: 

P. BLAKISTON, SON & CO., 

IOI2 WALNUT STREET. 

1891. 










Entered according to Act of Congress, in the year 1891, by 
P. BLAKISTON, SON & CO., 

In the office of the Librarian of Congress, at Washington, D. C. 




Press of Wm. F. Fell &. Co., 
1220-24 Sansom St., 
PHILADELPHIA. 







PREFACE TO SIXTH EDITION. 


It has been deemed advisable in the preparation of a Sixth Edition of 
the Compend to insert a number of additional paragraphs upon subjects 
which appeared to be of interest and importance to medical students. 

This has accordingly been done, with the result of increasing the size of 
the book some fifteen pages. It is hoped that the present edition will even 
more fully meet the needs of the student. 

ALBERT P. BRUBAKER. 


v 



PREFACE TO FIFTH EDITION. 


In the preparation of a Fifth Edition of the Compend of Physiology, 
the author has taken the opportunity to revise and rewrite a number of 
sections, to insert a few figures and to add some seventeen pages of new 
matter which, it is hoped, will further increase its usefulness to the student. 
While many of the changes that have been made will be found distributed 
throughout the body of the work, the principal additions will be found in 
the sections pertaining to the nervous system. 

Notwithstanding the many additions which have been made in this and 
previous editions, care has been taken to keep the Compend what it was 
originally intended to be, viz: A compact and convenient arrangement of 
the fundamental facts of human physiology. 

As most medical students enter upon the study of physiology before they 
have acquired a thorough knowledge of anatomy, it was thought desirable 
that such anatomical details should also be inserted as would be essential 
to a clear conception of the functions about to be studied. It is believed 
that it will be practically useful to students during their attendance upon 
lectures and in reviewing the subject prior to examinations. 

To those teachers of physiology who have kindly noticed and recom¬ 
mended the Compend to their students I tender my thanks, and trust that 
in its improved condition it will continue to merit their approval. 

ALBERT P. BRUBAKER. 


vi 



TABLE OF CONTENTS. 


PAGE 

Introduction,. 9 

Chemical Composition of the Body, . io 

Structural Composition of the Body,. 17 

Food,. 19 

Digestion,. 24 

Absorption,. 37 

Blood,. 45 

Circulation of Blood,. 51 

Respiration,. 59 

Animal Heat,. 67 

Secretion,. 69 

Mammary Glands,. 72 

Vascular or Ductless Glands,. 74 

Excretion,. 76 

Kidneys,. 76 

Liver,. 83 

Skin,. 88 

Nervous System,. 92 

Properties and Functions of Nerves,. 95 

Cranial Nerves,. 102 

Spinal Cord,. 116 

Spinal Nerves,. 118 

Medulla Oblongata,. 127 

Pons Varolii,. 131 

Crura Cerebri,..*. 131 

Corpora Quadrigemina,. 132 

Corpora Striata and Optic Thalami,. 133 

vii 






























TABLE OF CONTENTS. 


viii 

PAGE 

Cerebellum,. 134 

Cerebrum,. 136 

Sympathetic Nervous System,. 147 

Sense of Touch,. 151 

Sense of Taste,.•.. 152 

Sense of Smell,. 154 

Sense of Sight,. 154 

Sense of Hearing,. 165 

Voice and Speech,. 173 

Reproduction,. 176 

Generative Organs of the Female,. 176 

Generative Organs of the Male,. 179 

Development of Accessory Structures,. 180 

Development of the Embryo,. 185 

Table of Physiological Constants,. 191 

Table Showing Relation of Weights and Measures of the 
Metric System to Approximate Weights and Measures 

of the U. S.,. 194 

Index,. 195 



















COMPEND 

OF 

HUMAN PHYSIOLOGY. 


Physiology, from (pvcng, nature, and Aoyof, a discourse, in its original 
application embraced the study of all natural objects, inorganic as well as 
organic. In its modern application physiology signifies the study of life; 
the investigation of the vital phenomena exhibited by all organic bodies, 
vegetable and animal. 

It may be divided into— 

1. Vegetable physiology , which treats of the phenomena manifested by 
the several structures of which the plant is composed. 

2. Animal Physiology , which treats of the phenomena manifested by the 
organs and tissues of which the animal body is composed. 

Human Physiology is the study of the functions exhibited by the 
human body in a state of health. 

A function is the action of an organ or tissue. 

The Functions of the Human Body may be classified into three 
groups, viz.:— 

1. Nutritive functions, which have for their object the preservation of 
the individual; e. g., digestion, absorption, circulation of the blood, 
respiration, assimilation, animal heat, secretion and excretion. 

2. Animal functions, which bring the individual into conscious relation¬ 
ship with external nature; e. g., sensation, motion, language, mental 
and moral manifestations. 

2. Reproductive function , which has for its object the preservation of 
the species. 

The facts of human physiology have been determined by means of 
anatomy, chemistry, pathology, comparative anatomy, vivisection, the 
application of physics, etc. 

The body may be studied from a chemical and structural point of view. 

B 9 



10 


HUMAN PHYSIOLOGY. 


CHEMICAL COMPOSITION OF THE HUMAN 

BODY. 

By chemical analysis the solids and fluids of the body can be first 
reduced to a number of compound substances which are termed proximate 
principles: these again can be resolved by an ultimate analysis into fifteen 
chemical elements. The different chemical elements thus obtained, and 
the proportions in which they exist, are shown in the following table:— 


Oxygen . . 
Hydrogen . 
Nitrogen . 
Carbon . . 
Sulphur . . 

. 72.00 
. 9.10 
. 2.50 
. 13-50 
. -147 . 

Phosphorus 

. 1.15 • 

Calcium 

. 1.30 . 

Sodium . . 

. .10 . 

Potassium . 

. .026 , 

Magnesium 

.001 . 

Chlorine . 

•085 . 

Fluorine . . .08 . 

Iron.01 . 

Silicon ... a trace . 
Manganesium a trace . 


1 O.H. and C. are found in all the tissues and 

( fluids of the body, without exception. 

j O. H. C. and N. found in most of the fluids 

j and all tissues except fat. 

. In fibrin, casein, albumin, gelatin; as potas¬ 
sium sulpho-cyanide in saliva; as alkaline 
sulphate in urine and sweat. 

. In fibrin and albumin; in brain; as tri-sodium 
phosphate in blood and saliva, etc. 

. As calcium phosphate in lymph, chyle, blood, 
saliva, bones and teeth. 

. As sodium chloride in all fluids and solids of 
the body, except enamel; as sodium sulphate 
and phosphate in blood and muscles. 

. As potassium chloride in muscles; generally 
found with sodium as sulphates and phos¬ 
phates. 

. Generally in association with calcium, as phos¬ 
phate, in bones. 

. In combination with sodium, potassium and 
other bases, in all the fluids and solids. 

. As calcium fluoride in bones, teeth and urine. 

. In blood globules; as peroxide in muscles. 

. In blood, bones and hair. 

. Probably in hair, bones and nails. 


Of the four chief elements which together make up gy per cent, of the 
body, O. H. N. are eminently mobile , elastic , and possess great atomic heat. 
C. H. N. are distinguised for the narrow range and feebleness of their 
affinities and chemical inertia. C. has the greatest atomic cohesion. O. is 
noted for the number and intensity of its combinations, and its remarkable 
display of chemical activity. 

Chemical elements, with the exception of the gases, O. H. and N., 
do not exist alone in the body, but are combined in characteristic propor¬ 
tions to form compounds, the proximate principles , the ultimate compounds 
to which the fluids and solids can be reduced. 



CHEMICAL COMPOSITION OF THE HUMAN BODY. 11 

Proximate Principles exist in the body under their own form, and can 
be extracted without losing their distinctive properties. 

There are about one hundred proximate principles, which are divided 
into four classes, viz: inorganic , organic non-nitrogenized, organic nitro- 
genized , and principles of waste. 


I. INORGANIC PROXIMATE PRINCIPLES. 


SUBSTANCE. 

Oxygen,. 

Hydrogen,. 

Nitrogen, .. 

Carbonic anhydride, . . 
Carburetted hydrogen, | 
Sulphuretted hydrogen, / 

Water,. 

Sodium chloride, .... 
Potassium chloride, . . . 
Ammonium chloride, . . 
Calcium chloride, . . . 
Calcium carbonate, . . . 
Calcium phosphate, j 
Magnesium phosphate, [ 
Sodium phosphate, 
Potassium phosphate, J 
Sodium sulphate, ) 

Potassium sulphate, | 
Sodium carbonate, 1 
Potassium carbonate, J 
Magnesium carbonate, 


WHERE FOUND. 

Lungs and blood. 

Stomach and intestines. 

Blood and intestines. 

Expired air of lungs. 

Lungs and intestines. 

Found in all solids and fluids. 

In all fluids and solids except enamel. 

In muscles, liver, saliva, gastric juice, etc. 
Gastric juice, saliva, tears, urine. 

Bones, teeth, urine. 

Bones, teeth, cartilage, internal ear, blood. 
In all fluids and solids of the body. 


Universal except milk, bile and gastric juice. 

Bones, blood, lymph, urine, etc. 

Blood and sebaceous matter. 


Oxygen is one of the constituent elements of all the fluids and solids of 
the body. It is found in a free state in the respiratory passages and intesti¬ 
nal tract; it is held in solution in the lymph and plasma and forms a loose 
combination with the haemoglobin of the blood corpuscles. The function 
of the oxygen in the body appears to be the oxidation of albuminous, ole¬ 
aginous and saccharine compounds to their ultimate forms, urea, carbonic 
acid, water, etc. As to whether this is brought about by direct oxidation 
or by a fermentative process is yet unknown. As oxygen only enters into 
combination under a high temperature, it is assumed that it exists in the 
body under the form of ozone, 0 3 , which possesses remarkably active oxid¬ 
izing powers. The seat of oxidation is at present located in the tissues, as 
the presence of ozone in the blood has not been positively demonstrated. 

Hydrogen is also a constituent element of almost all the compounds of 
the body; it exists in a free state in the intestinal tract, where it is produced 









12 


HUMAN PHYSIOLOGY. 


by a decomposition of organic substances; it is also produced within the tis¬ 
sues as a result of chemical changes. Its function is unknown, though it is 
asserted by Hoppe-Seyler that hydrogen unites with neutral oxygen, 0 2 , in 
the tissues, forming water and liberating oxygen in the nascent state, which 
becomes the oxidizing agent. The process is represented in the following 
equation:— 

HH + O a + n = H 2 0 + On, 

in which n represents the oxidizable substance. 

Water is an essential constituent of all the tissues of the body, consti¬ 
tuting about 70 per cent, of the entire body weight. It is introduced into 
the body in the form of drink and as a constituent of all kinds of food. 
The average quantity consumed daily is about four pints. While in the 
body, water acts as a general solvent, gives pliability to various tissues, and 
promotes the passage of inorganic and organic matters through animal 
membranes. It also promotes chemical changes which are essential to 
absorption and assimilation of food and the elimination of products of 
waste. It is probable that water is also formed within the body by the 
union of oxygen with the surplus hydrogen of the food. It is eliminated 
by the skin, lungs and kidneys. 

Sodium chloride is present in all the solids and fluids of the body, with 
the exception of enamel. It regulates osmotic action, holds the albuminous 
principles of the blood in solution, and preserves the form and consistence 
of blood corpuscles and the cellular elements of the tissues, by regulating 
the amount of water entering into their composition. 

Calcium phosphate is the most abundant of all the inorganic principles 
with the exception of water, and is present to a great extent in bone, teeth, 
muscles and milk. It gives the requisite consistency and solidity to the 
different tissues and organs. In the blood, it is held in solution by the 
albuminous constituents. 

The Sodium and Potassium phosphates are present in most of the solids 
and fluids, and give to them their alkaline reaction. They are chiefly 
derived from the food. 

II. ORGANIC NON-NITROGENIZED PRINCIPLES. 

The organic non-nitrogenized principles are derived mainly from the 
vegetable world, but are also produced within the animal body. They are 
divided into : 1st, the carbo-hydrates , comprising starch and sugar, bodies 
in which the oxygen and hydrogen exist in the proportion to form water, 
the amount of carbon being variable; 2d, the fats , bodies having the same 


CHEMICAL COMPOSITION OF THE HUMAN BODY. 


13 


elements entering into their composition, but with the carbon and hydrogen 
increased and the oxygen diminished in amount; 3d, fatty acids; 4th, alco¬ 
hols. 

SUGARS. C. O. H. 

Glycogen, or Liver sugar. 

Lactose, or Milk sugar. 

Glucose, or Grape sugar. 

Inosite, or Muscle sugar. 

Sugar is found in many of the tissues and fluids of the body; eg., liver, 
milk, placenta, blood, muscles, etc. The varieties of sugar are soluble in 
water, assume the crystalline form upon evaporation, and are converted 
into alcohol and carbonic acid by fermentation. Sugar is derived from the 
food, converted, in the alimentary canal, into glucose, absorbed by the veins 
of the portal system, and then stored up in the liver, under the form of 
glycogen. When the system requires sugar, it is again returned to the cir¬ 
culation, and plays its part in the nutritive processes of the body. It is 
finally oxidized, and thus contributes to the formation of heat. It is finally 
eliminated under the form of carbonic acid and water. There is no experi¬ 
mental proof that sugar contributes directly to the formation of fat in the 
animal body. 

NEUTRAL FATS. C. O. H. 

Palmitin. 

Stearin. 

Olein. 

The Neutral fats , when combined in proper proportions, constitute a 
large part of the fatty tissue of the body; they are soluble in ether, chloro¬ 
form and hot alcohol; insoluble in cold alcohol and water, and liquefy at 
a high temperature; when a neutral fat is subjected to a high temperature 
in the presence of water and an alkali, it is decomposed, with the assimi¬ 
lation of the elements of water, into a fatty acid and glycerine. The fatty 
acid combines with the alkali and forms an oleate, palmitate or stearate, 
according to the fat used. A similar decomposition of the neutral fats is 
said to take place in the small intestine during digestion. When thoroughly 
mixed with pancreatic juice, the fats are reduced to a condition of emulsion , 
a state in which the fat is minutely subdivided and the small globules held 
in suspension. 

FATTY ACIDS. C. O. H. 

Palmitic acid. Propionic acid. 

Stearic acid. Butyric acid. 

Oleic acid. Caproic acid. 


14 


HUMAN PHYSIOLOGY. . 


The Fatty acids combined with sodium, potassium and calcium, are 
found as salts in various fluids of the body, such as blood, chyle, feces, 
etc. Phosphorized fats in nervous tissue, butyric acid in milk, propionic 
acid in sweat, are also constituents of the body. 

The Fats are derived from the food, both animal and vegetable. They 
are deposited in the form of small globules in the cells of the different 
tissues, are suspended in various fluids, are deposited in masses in and 
around various anatomical structures and beneath the skin. Independent 
of the fat consumed as food, there is good experimental evidence that fat 
is also produced within the animal body from a partial decomposition of 
the albuminous compounds. Fat serves as a non-conductor of heat, gives 
roundness and form to the body, and protects various structures from 
injury. The fats are ultimately oxidized, thus giving rise to heat and 
force, and are finally eliminated as carbonic acid and water. 

ALCOHOLS. 

Glycerine. Cholesterine. Alcohol. 

Glycerine is chemically a triatomic alcohol in combination with the neu¬ 
tral fats of the body. During pancreatic digestion it is set free. It is 
supposed by many physiologists to be directly concerned in the production 
of glycogen. Cholesterine is a crystallizable substance largely present in 
the bile, though it is found in other fluids and solids. It is supposed to be 
a waste product of nervous matter. Alcohol has been found in the urine. 
It is supposed to be the result of an alcoholic fermentation in the intestine. 

III. ORGANIC NITROGENIZED PRINCIPLES. 

The nitrogenized or proteid compounds are organic in their origin, being 
derived from the animal and vegetable world; they are taken into the body 
as food, appropriated by the tissues, and constitute their organic basis; they 
differ from the non-nitrogenized substances in not being crystalline, but 
amorphous, in having a more complex but just as definite composition, and 
containing in addition to C. O. H., nitrogen, with, at times, sulphur and 
phosphorus. The proteids possess characteristics which distinguish them 
from all other substances: viz., a molecular mobility , which permits isomeric 
modifications to take place with great facility; a catalytic influence , in 
virtue of which they promote, under favorable conditions, chemical changes 
in other substances: e.g., during digestion, salivin and pepsin cause starch 
and albumin to be transformed into sugar and albuminose respectively. 
Different proteids possess varying proportions of water, which they lose 


CHEMICAL COMPOSITION OF THE HUMAN BODY. 15 

when subjected to desiccation, becoming solid; but upon exposure to 
moisture they again absorb water, regaining their original condition—they 
are hygroscopic. Another property is that of coagulation , which takes 
place under certain conditions: e.g ., the presence of mineral acids, heat, 
alcohol, etc. 

After death the nitrogenized compounds undergo putrefactive changes, 
give rise to carburetted and sulphuretted hydrogen and other gases. In 
order that these changes may take place it is essential that certain condi¬ 
tions be present: viz., atmospheric air or some fluid containing oxygen, 
moisture , and a temperature varying between 6o° and 90° F. The cause 
of the putrefactive change is the presence of a minute unicellular organ¬ 
ism, the bacterium ter mo. 

The nitrogenized bodies found in the organism are quite numerous, and 
although they resemble each other in many particulars, there are yet 
important differences, and can be arranged into the following groups :— 

1. Native Albumins. —Proteid bodies soluble in water, many acids, and 
usually in alkalies; coagulable at a temperature of from 140° to 163° F. 

a. Serum Albumin , the principal form of albumin found in the animal 
fluids and solids. 

b. Egg albumin , not found in ordinary tissues, but present in white 
of egg. 

2. Globulins. —Proteid bodies insoluble in water, but soluble in solutions 
of sodium chloride. 

a. Globulin , found in many tissues, but largely present in crystalline 
lens. 

b. Myosin , found in the muscles in life in a fluid condition; after 
death it undergoes coagulation, giving rise to the rigidity of the 
muscles. 

c. Paraglobulin , present in blood and obtained from it by passing a 
stream of carbon dioxide through it; it is also precipitated by 
adding sodium chloride. 

d. Fibrinogen , present in serous fluid and blood, and can be precipi¬ 
tated by the prolonged use of carbon dioxide; it is also precipitated 
by the addition of 12 to 16 per cent, of sodium chloride. 

3. Derived Albumins. —Proteid bodies which are not coagulable by heat; 
insoluble in pure water and in salt solutions; soluble in both acid and 
alkaline solutions. 

a. Acid Albumin, found principally in the stomach during first stage 
of digestion, the result of the action of the hydrochloric acid upon 
the albumin of the food. 


16 


HUMAN PHYSIOLOGY. 


b. Alkali Albumin, found in the intestine during pancreatic digestion, 
the result of the action of alkalies upon the albumin of the food. 

c. Casein, the chief proteid of milk; it is precipitated by acetic acid 
and rennet. 

4. Peptones. —These bodies are formed in the stomach and intestinal 
tract by the action of the gastric and pancreatic juices upon the albumins 
of the food. They are very soluble in water, alkaline and acid solutions; 
non-coagulable by heat; very diffusible. They are precipitated by tannic 
acid and alcohol. 

5. Albuminoids. —The albuminoids are the results of various modifica¬ 
tions of albumins occurring during the nutritive process, as well as by 
the action of various external influences. 

a. Mucin, the characteristic ingredient of mucus secreted by the 
mucous membranes, giving to it its viscidity. 

b. Chondrin, found in cartilage. 

c. Gelatin, found in connective tissue, tendons, ligaments, bones, etc. 

d. Elastin, found in elastic tissue. 

e. Keratin, found in skin and epidermic appendages, nails,hair, horn, etc. 

6. Fibrin.— A filamentous albumin obtained by washing blood clots. It 
is insoluble in water and mineral acids. 

As the properties of the compounds formed by the union of elements are 
the resultants of the properties of the elements themselves, it follows that 
the ternary substances, sugars, starches and fats, possess a great inertia and 
a notable instability; while in the more complex albuminous compounds, 
in which sulphur and phosphorus are united to the four chief elements, 
molecular mobility, resulting in isomerism, exists in a high degree. As 
these compounds are unstable, of a greater molecular mobility, they are well 
fitted to take part in the composition of organic bodies, in which there is 


a continual movement of composition and decomposition. 




V 

IV. PRINCIPLES 

OF WASTE. 



Urea, 

Xanthin, 

Sodium, 



Creatin, 

Tyrosin, 

Potassium, 


- Urates. 

Creatinin, 

Hippuric Acid, 

Ammonium, 


Cholesterin, 

Calcium Oxalate, 

Calcium, 

, 



These principles which represent waste are of organic origin, arising 
within the body as products of disassimilation or retrograde metamorphosis 
of the tissues; they are absorbed by the blood, carried to the various 
excretory organs, and by them eliminated from the body. 

The excrementitious substances will be fully considered under excretion. 



STRUCTURAL COMPOSITION OF THE BODY. 17 

Proximate Quantity of the Chemical Elements and Proximate 
Principles of the Body, Weighing 154 lbs. 


lbs. oz.- lbs. oz. 

Oxygen, .ill . . Water,.111 

Hydrogen,.14 . . Albuminoids,.23 7 

Nitrogen,. 3 8 Fats,.12 

Carbon,.21 . . Calcium phosphate, ... 5 13 

Calcium,. 2 . . Calcium carbonate, ... 1 . . 

Phosphorus,. 1 12 Calcium fluoride,. 3 

Sodium, etc.,.12 Sodium sulphate, etc., . ... 9 


154 . . 154 • • 


STRUCTURAL COMPOSITION of THE BODY. 

The Study of the Structure of the body reveals that it is composed 
of dissimilar parts, e.g., bones, muscles, nerves, lungs, etc.; while these, 
again, by closer examination, can be resolved into elementary structures, 
the tissues , e.g., connective tissue, muscular, nervous, epithelial tissue, etc. 

Microscopical examination of the tissues shows that they are com¬ 
posed of fundamental structural elements, termed cells. 

Cells are living physiological units ; the simplest structural forms capable 
of manifesting the phenomena of life. 

Cells vary in their anatomical constitution in the different structures of 
the body, and may be classed in three groups, viz : 1. Cells possessing a 

distinct cell wall, cell substance and a nucleus. 2. Cells possessing a cell 
substance and a nucleus. 3. Cells possessing the cell substance only. 
They vary in size, from the to t ^ ie jb'U 0 f an inch in diameter; when 
young and free to move in a fluid medium they assume the spherical fotm; 
but when subjected to pressure, may become flattened, cylindrical, fusiform 
or stellate. 

Structure of Cells. The cell wall is not an essential structure, as 
many cells are entirely devoid of it. It is a thin, structureless, transparent 
membrane, permeable to fluids. 

The Cell Substance in young cells is a soft, viscid, albuminous matter, 
unstable, insoluble in water, and known as protoplasm, bioplasm, sarcode, 
etc.; in older cells the original cell substance undergoes various transform¬ 
ations, and is partly replaced by fat globules, pigment and crystals. 

The Nucleus is a small vesicular body in the interior of the cell sub¬ 
stance, and frequently contains smaller bodies, the nucleoli. 















18 


HUMAN PHYSIOLOGY. 


MANIFESTATIONS OF CELL LIFE. 

Growth. Cells when newly formed are exceedingly small, but as they 
approach maturity they increase in size, by the capability which the cells 
possess of selecting and appropriating new material as food, vitalizing and 
organizing it. The extent of cell growth varies in different tissues; in 
some the cells remain exceedingly small, in others they attain considerable 
size. In many instances the cell substance undergoes transformation into 
new compounds destined for some ulterior purpose. 

Reproduction. Like all organic structures cells have a limited period 
of life; their continual decay and death necessitates a capability of repro¬ 
duction. Cells reproduce themselves in the higher animals mainly by 
fission. This is seen in the white blood corpuscles of the young embryos 
of animals; the corpuscle here consists of a cell substance and nucleus. 
When division of the cell is about to take place, the nucleus elongates, the 
cell substance assumes the oval form, a constriction occurs, which gradually 
deepens, until the original cell is completely divided and two new cells are 
formed, each of which soon grows to the size of the parent cell. 

In cells provided with a cell membrane the process is somewhat different. 
In the ova of the inferior animals, after fertilization has taken place, a 
furrow appears on the opposite sides of the cell substance, which deepens 
until the cell is divided into two equal halves, each containing a nucleus; 
this process is again repeated until there are four cells, then eight, and so 
on until the entire cell substance is divided into a mulberry mass of cells, 
completely occupying the interior of the cell membrane. The whole pro¬ 
cess of segmentation takes place with great rapidity, occupying not more 
than a few minutes, in all probability. 

Mption. Spontaneous movement has been observed in many of the 
cells of the body. It may be studied, for example, in the movements of 
the spermatozoids, the waving of the cilia covering the cells of the bronchial 
mucous membrane, the white corpuscles of the blood, etc. 

By a combination and transformation of these original structural elements, 
and material derived from them, all the tissues are formed which enter into 
the structure of the human body. 

CLASSIFICATION OF TISSUES. 

I. Homogeneous Substance, a more or less solid, albuminous struc¬ 
ture, filling the spaces between the cells and fibres of various tissues, e.g ., 
cartilage, bone, dentine, etc. 

II. Limiting Membrane, a thin homogeneous membrane, structureless, 


FOOD. 


19 


composed of coagulated albumin, and often not more than the °f an 

inch in thickness, found lining the blood vessels and lymphatics, forming 
the basement membrane of the skin and mucous membranes, the posterior 
layer of the cornea, the capsule of the crystalline lens, etc. 

III. Simple fibrous or filamentous tissue—the elements of which 
are real or apparent filaments. 

(a) Connective or areolar; white fibrous tissue; constituting tendons, 
ligaments, aponeuroses, periosteum, dura mater, synovial membranes, 
vascular tunics, etc. 

(b) Yellow elastic tissue; found in the middle coats of arteries, veins, 
lymphatics, ligamentum nuchae, vocal cords, ligamenta subflava, etc. 

IV. Compound membranes (membrano-cellular or fibro-cellular 
tissues), cells aggregated into laminae. 

(a) Epidermic tissue; (b) epithelial tissue; (c) glandular tissue; (d) 
cornea. 

V. Cells containing coloring matter, or pigment cells, e. g., skin, 
choroid membrane, etc. 

VI. Cells coalesced or consolidated by internal deposits, e. g., 

hair, nails, bone, teeth, etc. 

VII. Cells imbedded in an intercellular substance, e. g., cartilage, 
crystalline lens, etc. 

VIII. Cells aggregated in clusters, forming tissues more or less solid, 
e. g., adipose tissue, lymphatic glands. 

IX. Cells imbedded in a matrix of capillaries, e. g., gray or vesicular 
nervous matter. 

X. Cells whose coalesced cavities form tubes containing liquids or 
secondary solid deposits, e. g., vascular tissue, dentine. 

XI. Cells free, isolated, or floating—fluid tissue— e. g., red and white 
blood corpuscles, lymph and chyle corpuscles. 


FOOD. 

A Food may be defined to be any substance capable of playing a part 
in the nutrition of the body. 

Food is required for the repair of the waste of the tissues consequent on 
their functional activity, for the generation of heat and the evolution of force. 
Hunger and Thirst are sensations which indicate the necessity for 


20 


HUMAN PHYSIOLOGY. 


taking food; they arise in the tissues at large, and are referred to the 
stomach and fauces, respectively, through the sympathetic nervous system. 

Inanition or Starvation results from an insufficiency or absence of 
food, the physiological effects of which are hunger, intense thirst, intestinal 
uneasiness, weakness and emaciation; the quantity of carbonic acid ex¬ 
haled diminishes and the urine is lessened in amount; the volume of the 
blood diminishes; a fetid odor is exhaled from the body; vertigo, stupor 
followed by delirium, and at times convulsions, result from a disturbance 
of the nerve centres; a marked fall of the bodily temperature occurs, from 
a diminished activity of the nutritive process. Death usually takes place, 
from exhaustion. 

During starvation the loss of different tissues, before death occurs, aver- 
ages T 4 ^, or 40 per cent, of their weight. 

Those tissues which lose more than 40 per cent, are fat, 93.3 ; blood, 75; 
spleen, 71.4; pancreas, 64.1; liver, 52; heart, 44.8; intestines, 42.4; 
muscles, 42.3. Those which lose less than 40 per cent, are the muscular 
coat of the stomach, 39.7; pharynx and oesophagus 34.2; skin, 33.3; 
kidneys, 31.9; respiratory apparatus, 22.2; bones, 16.7; eyes, 10; nervous 
system, 1.9. 

The Fat entirely disappears, with the exception of a small quantity 
which remains in the posterior portion of the orbits and around the kid¬ 
neys. The Blood diminishes in volume and loses its nutritive properties. 
The Muscles undergo a marked diminution in volume and become soft and 
flabby. The Nervous system is last to suffer, not more than two per cent, 
disappearing before death occurs. 

The appearances presented by the body after death from starvation are 
those of anaemia and great emaciation; almost total absence of fat; blood¬ 
lessness; a diminution in the volume of the organs; an empty condition 
of the stomach and bowels, the coats of which are thin and transparent. 
There is a marked disposition of the body to undergo decomposition, 
giving rise to a very fetid odor. 

The duration of life after a complete deprivation of food varies from 
eight to thirteen days, though life can be maintained much longer if a 
quantity of water be obtained. The water is more essential under these 
circumstances than the solid matters, which can be supplied by the organism 
itself. 

The food consumed daily is a heterogeneous compound consisting of 
both nutritious and innutritious portions. The nutritious portions are 
known as the alimentary principles, while the food, as a whole, is known 
as aliment. 


FOOD. 


21 


The different alimentary principles which are appropriated by the system 
are combined in different proportions in the various articles of food, and 
are separated from the innutritious substances during the process of diges¬ 
tion. They belong to the organic and inorganic worlds, and may be 
classified, according to their chemical composition, as follows:— 

CLASSIFICATION OF ALIMENTARY PRINCIPLES. 

1. Albuminous group—nitrogenized, C. O. H. N. S. P. 

PRINCIPLE. WHERE FOUND. 

Myosin, syntonin, .Flesh of animals. 

Vitellin , albumin ,.Yolk of egg, white of egg. 

Fibrin , globulin ,.Blood contained in meat. 

Casein ,.Milk, cheese. 

Gluten ..Grain of wheat and other cereals. 

Vegetable albumin ,.Soft growing vegetables. 

Legumin ,.Peas, beans, lentils, etc. 

Gelatin ..Bones. 

2. Saccharine group—non-nitrogenized, C. O. H. 

Cane sugar, beet root sugar , . . Sugar cane, beets, etc. 

Glucose, grape sugar ,.Fruits. 

Inosite, liver sugar, glycogen, . Muscles, liver, etc. 

Lactose or milk sugar, .... Milk. 

Starch ,.Cereals, tuberous roots and leguminous 


plants. 


3. Oleaginous group—non-nitrogenized, C. O. H. 

Found in the adipose tissue of animals, 



seeds, grains, nuts, fruits, and other 
vegetable tissues. 


4. Inorganic group. Water, sodium and potassium chlorides, sodium, 
calcium, magnesium and potassium phosphates, calcium carbonate and iron. 

5. Vegetable acid group. Malic, citric, tartaric and other acids, 
found principally in fruits. 

6. Accessory foods. Tea, coffee, alcohol, cocoa, etc. 

The Albuminous principles enter largely into the composition of the 
body, and constitute the organic bases of the different tissues; they are 
mainly required for the growth and repair of the tissues. There is good 
reason to believe that the albuminous principles are decomposed in the 
body into fat and urea, and the former when oxidized gives rise to the 
evolution of heat and force, while the latter is eliminated by the kidneys. 
Muscular work, however, does not result from a destruction of the albu¬ 
minous compounds. The oxidation of the carbonaceous compounds, sugars 













22 


HUMAN PHYSIOLOGY. 


and oils, furnishing the force which is transformed by the muscular system 
into motor power. When employed exclusively as food for any length of 
time, the albuminous substances are incapable of supporting life. 

The Saccharine principles are important to the process of nutrition, but 
the changes which they undergo are not fully understood; they form but a 
small proportion of the animal tissues, and by oxidation generate heat and 
force. Starch undergoes conversion into dextrin and grape sugar. 

The Oleaginous principles form a large part of the tissues of the body. 
They are introduced into the system as food, and are formed also from a 
transformation of albuminous matter during the nutritive process; they 
enter into the composition of nervous and muscular tissue, and are stored 
up as adipose tissue in the visceral cavities and subcutaneous connective 
tissue, thus giving roundness to the form and preventing, to some extent, 
the radiation of heat. While they aid in the reconstruction of tissue, they 
mainly undergo oxidation, giving rise to the production of heat and the 
evolution of muscular and nervous force. 

The Inorganic principles constitute an essential part of all animal tissues, 
and are introduced with the food. 

Water is present in all fluids and solids of the body, holding their 
ingredients in solution, promoting the absorption of new material into the 
blood and tissues, and the removal of waste ingredients. 

Sodium chloride is an essential constituent of all tissues, regulating the 
passage of fluids through animal membranes (endosmosis and exosmosis). 

Calcium phosphate gives solidity to bones and teeth, constituting more 
than one-half their substance. 

Iron is a constituent of the coloring matter of the blood. 

The Vegetable acids are important to nutrition, and tend to prevent the 
scorbutic diathesis. 

The Accessory foods also influence the process of nutrition. Tea excites 
the respiratory function, increasing the elimination of carbonic acid. Coffee 
is a stimulant to the nervous system; increases the force of the heart’s 
action, increases the arterial tension and retards waste. 

Alcohol, when introduced into the system in small quantities, undergoes 
oxidation and contributes to the production of force, and is thus far a food. 
It excites the gastric glands to increased secretion, improves the digestion, 
accelerates the action of the heart and stimulates the activities of the 
nervous centres. In zymotic diseases, and all cases of depression of the 
vital powers, it is most useful as a restorative agent. When taken in 
excessive quantities, it is eliminated by the lungs and kidneys. The meta¬ 
morphosis of the tissue is retarded, the elimination of urea and carbonic 


FOOD. 


23 


acid is lessened, the temperature lowered, the muscular powers impaired 
and the resistance to depressing external influences diminished. When 
taken through a long period of time, alcohol impairs digestion, produces 
gastric catarrh, disorders the secreting power of the hepatic cells. It also 
diminishes the muscular power and destroys the structure and composition 
of the cells of the brain and spinal cord. The connective tissue of the body 
increases in amount, and subsequently contracting, gives rise to sclerosis. 

A proper combination of different alimentary principles is essential 
for healthy nutrition; no one class being capable of maintaining life for 
any definite length of time. 

The Albuminous food in excess promotes the arthritic diathesis, mani- 
fecting itself as gout, gravel, etc. 

The Oleaginous food in excess gives rise to the bilious diathesis, while a 
deficiency of it promotes the scrofulous. 

The Farinaceous food, when long continued in excess, favors the rheu¬ 
matic diathesis by the development of lactic acid. 

The Alimentary Principles are not introduced into the body as such, 
but are combined in proper proportions to form compound substances, 
termed foods , e . g., bread, milk, eggs, meat, etc., the nutritive value of each 
depending upon the extent to which these principles exist. 


PERCENTAGE COMPOSITION OF DIFFERENT FOODS. 



WATER. 

ALBUMIN. 

STARCH. 

SUGAR. 

FATS. 

SALTS. 

Bread, .... 

. 37 

8.i 

47-4 

3-6 

1.6 

2-3 

Milk, .... 

. 86 

4.1 

. 

5-2 

3-9 

0.8 

Eggs, .... 

• 74 

14.0 

. . 

. . 

10.5 

i -5 

Meat, .... 

• 54 

27.6 

. * 

. . 

1545 

2-95 

Potatoes, . . . 

. 75 

2.1 

18.8 

3-2 

0.2 

0.7 

Corn, .... 
Oatmeal, . . . 

• 14 

11.1 

64.7 

0.4 

8.1 

i -7 

. 15 

12.6 

58.4 

5-4 

5-6 

3 

Turnips, . . . 

. 9 i 

1.2 

5 -i 

2.1 

. . 

6 

Carrots, . . . 

.83 

i -3 

8.4 

6.1 

0.2 

1.0 

Rice, .... 

• 13 

6-3 

79.1 

0.4 

0.7 

o -5 


The amount of food required in 24 hours is estimated from the total 
quantity of carbon and nitrogen excreted from the body in 24 hours; these 
two elements representing the waste or destruction of the carbonaceous and 
nitrogenized compounds. It has been determined by experimentation that 
about 4600 grains of carbon and about 300 grains of nitrogen are elimi¬ 
nated from the body daily; the ratio being about 15 to 1. That the body 
may be kept in its normal condition, a proper proportion of carbonaceous 
(bread) to nitrogenized (meat) food should be observed in the diet. 







24 


HUMAN PHYSIOLOGY. 


The method of determining the proper amounts of both kinds of food is 
as follows:— 

iooo grains of bread (2 oz.) contain 300 grs. C. and 10 grs. N. 

To obtain the requisite amount of nitrogen from bread, 30,000 grains, 
or about 4 lbs., containing 9000 grains of carbon and 300 of nitrogen, 
would have to be consumed. Under such a diet there would be a large 
excess of carbon, which would be undesirable. On a meat diet the reverse 
obtains:— 

1000 grains of meat (2 oz.) contain 100 grs. C. and 30 grs. N. 

To obtain the requisite amounts of carbon from meat, 45,000 grains, or 
about lbs., containing 4500 grains of carbon and 1350 grains of nitro¬ 
gen, would have to be consumed. Under such circumstances there would 
arise an excess of nitrogen in the system, which would be equally undesir¬ 
able and injurious. By combining these two articles, however, in proper 
proportion, the requisite amounts of carbon and nitrogen can be obtained 
without any excess of either, e. g. :— 

2 lbs. of bread contain 4630 grs. C. and 154 grs. N. 

% u meat « 463 “ “ “ 154 “ “ 

5093 C. 308 N. 

The amount of carbon and nitrogen necessary to compensate for the loss 
to the system daily would be contained in the above amount of food. As 
about 3^ oz. of oil or butter are consumed daily, the quantity of bread can 
be reduced to 19 oz. In the quantities of bread and meat above mentioned, 
there are 4.2 oz. albumin, 9.3 sugar and starch. 


DIGESTION. 

Digestion is a physical and chemical process, by which the food intro¬ 
duced into the alimentary canal is liquefied and its nutritive principles 
transformed by the digestive fluids into new substances capable of being 
absorbed into the blood. 

The Digestive Apparatus consists of the alimentary canal and its 
appendages, viz.: teeth, salivary, gastric and intestinal glands, liver and 
pancreas. 

Digestion maybe divided into seven stages: prehension, mastication, 
insalivation, deglutition, gastric and intestinal digestion and defecation. 




DIGESTION. 25 

Prehension, the act of conveying food into the mouth, is accomplished 
by the hands, lips and teeth. 

Mastication is the trituration of the food, and is accomplished by the 
teeth and lower jaw, under the influence of muscular contraction. When 
thoroughly divided, the food presents a greater surface for the solvent 
action of the digestive fluids, thus aiding the general process of digestion. 

The Teeth are thirty-two in number, sixteen in each jaw, and divided 
into four incisors or cutting teeth, two canines, four bicuspids, and six 
molars or grinding teeth; each tooth consists of a crown covered by 
enamel, a neck, and a root surrounded by the crusta petrosa, and imbedded 
in the alveolar process ; a section through a tooth shows that its substance 
is made of dentine, in the centre of which is the pulp cavity, containing 
blood vessels and nerves. 

The lower jaw is capable of making a downward and an upward, a 
lateral and an antero-posterior movement, dependent upon the construction 
of the temporo-maxillary articulation. 

The jaw is depressed by the contraction of the digastric , genio-hyoid, 
mylo-hyoid and platysma my aides muscles; elevated by the temporal , 
masseter and internal pterygoid muscles; moved laterally by the alternate 
contraction of the external pterygoid muscles; moved anteriorly by the 
■bterygoid and posteriorly by the united actions of the genio-hyoid , mylo¬ 
hyoid and posterior fibres of the temporal muscle. 

The food is kept between the teeth by the intrinsic and extrinsic mus¬ 
cles of the tongue from within, and the orbicularis oris and buccinator 
muscles from without. 

The Movements of Mastication, though originating in an effort of 
the will and under its control, are, for the most part, of an automatic or 
reflex character, taking place through the medulla oblongata and induced 
by the presence of food within the mouth. The nerves and nerve centres 
involved in this mechanism are shown in the following table :— 


NERVOUS CIRCLE OF MASTICATION. 

AFFERENT OR EXCJTOR NERVES. EFFERENT OR MOTOR NERVES. 

1. Lingual branch of 5th pair. 1. 3d branch of 51b pair. 

2. Glosso-pharyngeal. 2. Hypo-glossal. 

3. Facial. 

The impressions made upon the terminal filaments of the sensory nerves 
are transmitted to the medulla; motor impulses are here generated which 


c 


26 


HUMAN PHYSIOLOGY. 


are transmitted through motor nerves to the muscles involved in the move¬ 
ments of the lower jaw. The medulla not only generates motor impulses, 
but coordinates them in such a manner that the movements of mastication 
may be directed toward the accomplishment of a definite purpose. 

Insalivation is the incorporation of the food with the saliva secreted 
by the parotid , sub-maxillary and sub-lingual glands ; the parotid saliva, 
thin and watery, is poured into the mouth through Steno’s duct; the sub- 
maxillary and sub-lingual salivas, thick and viscid, are poured into the 
mouth through Wharton’s and Bartholini’s ducts. 

In their minute structure the salivary glands resemble each other. They 
belong to the racemose variety, and consist of small sacs or vesicles, 
which are the terminal expansions of the smallest salivary ducts. Each 
vesicle or acinus consists of a basement membrane surrounded by blood 


Fig. i. 




CELLS OF THE ALVEOLI OF A SEROUS OR WATERY SALIVARY GLAND. 

A. After rest. B. After a short period of activity. C. After a prolonged period of 
activity .—From Yeo’s Text-Book of Physiology. 

vessels and lined with epithelial cells. In the parotid gland the lining cells 
are granular and nucleated; in the sub-maxillary and sub-lingual glands the 
cells are large, clear and contain a quantity of mucigen. During and after 
secretion very remarkable changes take place in the cells lining the acini, 
which are in some way connected with the essential constituents of the 
salivary fluids. 

In a living serous gland, e. g., parotid, during' rest, the secretory cells 
lining the acini of the gland are seen to be filled with fine granules, which 
are often so abundant as to obscure the nucleus and enlarge the cells until 
the lumen of the acinus is almost obliterated (Fig. i). When the gland 
begins to secrete the saliva, the granules disappear from the outer boundary 
of the cells which then become clear and distinct. At the end of the 
secretory activity,' the cells have become free of granules, have become 
smaller and more distinct in outline. It would seem that the granular 




DIGESTION. 


27 


matter is formed in the cells during the rest, and discharged into the ducts 
during the activity of the gland. 

In the mucous glands, e.g. } sub-maxillary and sub-lingual, the changes 
that occur in the cells are somewhat different (Fig. 2). During the inter¬ 
vals of digestion, the cells lining the gland are large, clear and highly 
refractive, and contain a large quantity of mucigen. After secretion has 
taken place, the cells exhibit a marked change. The mucigen cells have 
disappeared, and in their place are cells which are small, dark and com¬ 
posed of protoplasm. It would appear that the cells, during rest, elabor¬ 
ate the mucigen which is discharged into the tubules during secretory 
activity, to become part of the secretion. 


Fig. 2. 



SECTION OF A “MUCOUS” GLAND. 

A. In a state of rest. B. After it has been for some time actively secreting .—After 

Lavdowsky. 


Saliva is an opalescent, slightly viscid, alkaline fluid, having a specific 
gravity of 1.005. Microscopical examination reveals the presence of 
salivary corpuscles and epithelial cells. Chemically it is composed of 
water, proteid matter, a ferment ( ptyalin ) and inorganic salts. The amount 
secreted in 24 hours is about 2lbs. Its function is twofold :— 

1. Physical .—Softens and moistens the food, glues it together, and 
facilitates swallowing. 

2. Chemical .—Converts starch into grape sugar. This action is due 
to the presence of the organic ferment, ptyalin. Ptyalin is an amorphous 
nitrogenized substance, which can be precipitated from the saliva by calcium 
phosphate. Its power of converting starch into grape sugar is manifested 
most decidedly at the temperature of the living body and in a slightly 


28 


HUMAN PHYSIOLOGY. 


alkaline medium. The change consists in the assumption of a molecule 
of water. 

Starch. Water. Grape Sugar. 

c 6 h 10 o 5 + h 2 o = c 6 h 12 o 6 

NERVOUS CIRCLE OF INSALIVATION. 

AFFERENT OR EXCITOR NERVES. EFFERENT OR MOTOR NERVES. 

1. Lingual branch of 5th pair. 1. Auriculo-temporal branch of 5th 

2. Glosso-pharyngeal. pair, for parotid gland. 

2. Chorda tympani, for sub-maxil¬ 
lary and sub lingual glands. 

The centres regulating the secretion are two, viz.: The medulla oblon¬ 
gata and the submaxillary ganglion of the sympathetic; the latter acting 
antagonistically to the former. Impressions excited by the food in the 
mouth reach the medulla oblongata through the afferent nerves; motor im¬ 
pulses are there generated which pass outward through the efferent nerves. 

Stimulation of the auriculo-temporal branch increases the flow of saliva 
from the parotid gland; division arrests it. 

Stimulation of the chorda tympani is followed by a dilation of the blood 
vessels of the sub-maxillary gland, increased flow of blood (thus acting as 
a vaso-dilator nerve) and an abundant discharge of a thin saliva; division 
of the nerve arrests the secretion. 

Stimulation of the cervical sympathetic is followed by a contraction of 
the blood vessels, diminishing the flow of blood (thus acting as a vaso-con- 
strictor nerve) and a diminution of the secretion, which now becomes thick 
and viscid; division of the sympathetic does not, however, completely 
dilate the vessels. There is evidence of the existence of a local vaso¬ 
motor mechanism, which is inhibited by the chorda tympani; exalted by 
the sympathetic. 

Deglutition is the act of transferring food from the mouth into the 
stomach, and may be divided into three stages :— 

1. The passage of the bolus from the mouth into the pharynx. 

2. From the pharynx into the oesophagus. 

3. From the oesophagus into the stomach. 

In the 1st stage, which is entirely voluntary, the mouth is closed and 
respiration momentarily suspended; the tongue, placed against the roof 
of the mouth, arches upward and backward, and forces the bolus into the 
fauces. 

In the 2d stage, which is entirely reflex, the palate is made tense and 
directed upward and backward by the levatores-palati and tensores-palati 


DIGESTION. 29 

muscles; the bolus is grasped by the superior constrictor muscle of the 
pharynx and rapidly forced into the oesophagus. 

The food is prevented from entering the posterior nares by the uvula 
and the closure of the posterior half-arches (the palato pharyngei muscles); 
from entering the larynx by its ascent under the base of the tongue and 
the action of the epiglottis. 

In the 31I stage , the longitudinal and circular muscular fibres, contracting 
from above downward, strip the bolus into the stomach. [For nervous 
mechanism of Deglutition, see Medulla Oblongata.] 

Gastric Digestion. The stomach is a dilation of the alimentary canal, 
13 inches long, 5 inches deep, having a capacity of about 5 pints; there 
can be distinguished a cardiac and pyloric orifice, a greater and lesser 
curvature, a greater and lesser pouch. 

It possesses three coats :— 

1. Serous, a reflection of the peritoneum. 

2. Muscular, the fibres of which are arranged longitudinally, transversely 
and obliquely. 

3. Mucous, thrown into folds, forming the rugae. 

Imbedded in the mucous coat are immense numbers of mucous and 
true gastric glands. In the pyloric end of the stomach are found the 
mucous glands, which are lined with columnar epithelium throughout their 
extent. In the cardiac end are found the true peptic glands (Fig. 3), the 
ducts of which are also lined with columnar cells, while the secretory parts 
are lined with two distinct varieties of cells. One variety consists of small 
spheroidal, granular cells, which border the lumen of the gland, and are 
known as the chief cells; the other variety consists of large, oval, well- 
defined granular cells, much less abundant, and are situated between the 
basement membrane of the gland and the chief cells. From their position 
they have been termed parietal cells. During the intervals of digestion the 
chief cells are pale, and the hyaline substance of which they are composed 
is finely granular. During the stage of active secretion the cells become 
swollen and turbid, and are then said to be rich in pepsin. Toward the 
end of digestion the granules disappear, the cells become pale and return to 
their former size. 

During the intervals of digestion, the mucous membrane of the stomach 
is pale and covered with a layer of mucus. Upon the introduction of food, 
the blood vessels dilate and become filled with blood, and the mucous 
membrane becomes red. At the same time small drops of a fluid, the 
gastric juice, begin to exude upon its surface, which gradually run together 
and trickle down the sides of the stomach. 


30 


HUMAN PHYSIOLOGY. 


The secretion of gastric juice is a reflex act, taking place through the 
central nervous system and called forth in response to the stimulus of food 
in the stomach. That the central nervous system also directly influences 
the production of the secretion is shown by the fact that mental emotion, 
such as fear and anger, will arrest or vitiate the normal secretion. The 
reflex nature of the process can be shown by experimentation upon the 
pneumogastric nerve. If during digestion, when the peristaltic movements 


Fig. 3. 



Diagram showing the relation of the ultimate twigs of the blood vessels, V and A, and 
of the absorbent radicles to the glands of the stomach and the different kinds of epi¬ 
thelium, viz., above cylindrical cells: small, pale cells in the lumen, outside which 
are the dark ovoid cells.— From Yeo’s Text-Book 0/ Physiology. 


are active and the gastric mucous membrane flushed and covered with 
gastric juice, the pneumogastric nerves are divided on both sides, the 
mucous membrane becomes pale, the secretion is arrested and the peristaltic 
movements become less marked. Stimulation of the peripheral end produces 
no constant effects; stimulation of the central end, however, is at once 
followed by dilatation of the vessels, flushing of the mucous membrane and 
a re-establishment of the secretion. It is evident, therefore, that during 








DIGESTION. 


31 


digestion afferent impulses are passing up the pneumogastrics to the medulla; 
efferent impulses, in all probability, pass through the fibres of the sym¬ 
pathetic nervous system to the blood vessels and glands concerned in the 
elaboration of the gastric juice. After all the nervous connections of the 
stomach are divided, a small quantity of juice continues to be secreted for 
several days. This has been attributed to the action of a local nervous 
mechanism and to the direct action of the food upon the protoplasm of the 
secreting cells. 

The Gastric Juice is a secretion of the true peptic glands, and when 
obtained from the stomach through a fistulous opening, is a clear, straw- 
colored fluid, decidedly acid, with a specific gravity of 1.005 to 1.010. 

COMPOSITION OF GASTRIC JUICE. 


Water,.975.00 

Pepsin,.15.00 

Hydrochloric acid,. 4.78 

Inorganic salts, .... 5-22 


1000.00 

The water forms the largest part of the fluid, and holds in solution the 
other ingredients. It results from a transudation from the blood vessels 
under the increased blood supply. Of the inorganic salts the chlorides of 
sodium and potassium are the most abundant. 

Pepsin is the organic nitrogenized ferment of the gastric juice, and is 
formed, during the intervals of digestion, by the peptic cells. In the 
presence of a small per cent, of an acid, it acquires the property of con¬ 
verting the albumin of the food into albuminose or peptones. 

Hydrochloric acid is present in small quantity, and gives the juice its 
acidity. In all probability, its production is due to the activity of the 
parietal cells. These two characteristic ingredients of the gastric juice 
exist in a state of combination as hydrochloro-peptic acid, and the presence 
of both is absolutely essential for the complete digestion of the food. 

When the food enters the stomach, it is subjected to the peristaltic action 
of the muscular coat, and thoroughly incorporated with the gastric juice. 
This fluid has a twofold action upon the food:—1st. A physical action, by 
which the fibrous tissues of meats, the cellulose and hard parts of grains 
and vegetables, are dissolved away until the food is disintegrated and 
reduced to the liquid condition. 2d. A chemical action, by which the 
albuminous principles are transformed into peptones. The more important 
foods with their contained albuminous principles are shown on page 21. 







32 


HUMAN PHYSIOLOGY. 


Upon meat the gastric juice has a decidedly disintegrating action. The 
connective tissue is first dissolved, the fibres are separated, the sarcolemma 
softened, and the whole reduced to a grumous, pultaceous mass. Milk 
undergoes coagulation in from ten to fifteen minutes, the casein being 
precipitated in the form of soft flocculi, which are easy of transformation 
into peptone. Upon Vegetable tissues , the gastric juice exerts also a dis¬ 
integrating action; the cellulose and woody fibres are dissolved and the 
nutritive principles liberated. Bread undergoes liquefaction quite readily. 

The Principal Action of the gastric juice, however, is to transform the 
different albuminous principles of the food into peptones or albuminose , the 
different stages of which are due to the acid and pepsin respectively. When 
freed from its combination, the hydrochloric acid converts the albumin 
into acid albumin or parapeptone ; while this intermediate product is being 
formed, the pepsin converts it at once into peptone. In order that the 
digestion of albumin may be complete, it is necessary that both the acid 
and pepsin be present in proper quantity. Before digestion, the albuminous 
principles are insoluble in water and incapable of being absorbed. After 
digestion, they become soluble and are readily absorbed. Peptones differ 
from the albumins in being— 

1. Diffusible, passing rapidly through the mucous membrane and walls 
of the blood vessels. 

2. Non-coagulable by heat, nitric or acetic acids; but are readily precipi¬ 
tated by tannic acid. 

3. Soluble in water and saline solutions. 

4. Assimilable by the blood ; when injected into it, they do not reappear 
in the urine. 

Gastric juice exerts no influence either upon grape sugar, cane sugar, 
starch or fat. 

Gastric Digestion occupies on the average from 3 to 5 hours, but 
varies in duration according to the nature and quantity of the food, exercise, 
temperature, etc. 

The Amount of gastric juice secreted in 24 hours varies, under normal 
conditions, from 8 to 14 pounds. 

Movements of the Stomach. As soon as digestion commences, the 
cardiac and pyloric orifices are closed; the walls of the stomach contract 
upon the food, and a peristaltic action begins, which carries the food along 
the greater and lesser curvatures, and thoroughly incorporates it with the 
gastric juice. As soon as any portion of the food is digested, it passes 
through the pylorus into the intestine. 


DIGESTION. 


33 


TABLE SHOWING DIGESTIBILITY OF VARIOUS ARTICLES 

OF FOOD. 


HOURS. 

Eggs, whipped,.i 

“ soft boiled,.3 

“ hard boiled,.3 

Oysters, raw,.2 

“ stewed,.3 

Lamb, broiled,.2 

Veal, broiled,.4 

Pork, roasted,.5. 

Beefsteak, broiled,.3 

Turkey, roasted,. .... 2 

Chicken, boiled,.4 

“ fricasseed,.2 

Duck, roasted,.4 

Soup, barley, boiled,.1 

“ beans, “ 3 

“ chicken, “ 3 

“ mutton, “ 3 

Liver, beef, broiled,.2 

Sausage, “ 3 

Green corn, boiled,.3 

Beans, “ 2 

Potatoes, roasted,.2 

“ boiled,.3 

Cabbage, “ 4 

Turnips, “ 3 

Beets, “ 3 

Parsnips, “ 2 


MINUTES. 

20 


30 

55 

30 

30 

15 

25 

45 

30 


30 

20 

45 

30 

30 

30 

30 

30 

45 

30 


Vomiting. The act of vomiting is usually preceded by nausea and a 
discharge of saliva into the mouth. This is then swallowed, and carries 
into the stomach a quantity of air which facilitates the ejection of the con¬ 
tents of the stomach by aiding the relaxation of the cardiac sphincter. A 
deep inspiration is then taken, during which the lower ribs are drawn in 
and the diaphragm descends and remains contracted. At the same time 
the glottis is closed. A sudden expiratory effort is now made, and the cardiac 
orifice being open, the abdominal muscles contracting, press upon the 
stomach and forcibly eject its contents into the mouth. 

Intestinal Digestion. The intestine is about 20 feet long, i]/ z inches 
in diameter, and possesses three coats :— 

1. Serous (peritoneal). 

2. Muscular, the fibres of which are arranged longitudinally and trans¬ 
versely. 

3. Mucous, thrown into folds, forming the valvulce conniventes. 





























34 


HUMAN PHYSIOLOGY. 


This stage of digestion is probably the most complex and important; here 
the different alimentary principles are further elaborated and prepared for 
absorption into the blood by being acted upon by the intestinal juice, pan¬ 
creatic juice and bile. 

Throughout the mucous coat are imbedded the intestinal follicles, the 
glands of Brunner and Lieberkuhn. They secrete the true intestinal juice, 
which is an alkaline, viscid fluid, composed of water, organic matter and 
salts. Its function is to convert starch into glucose, and assist in the diges¬ 
tion of the albuminoids. 

The Pancreatic Juice is secreted by the pancreas, a flattened gland 
about six inches long, running transversely across the posterior wall of the 
abdomen, behind the stomach; its duct opens into the duodenum. 


Fig. 4. 



ONE SACCULE OF THE PANCREAS OF THE RABBIT IN DIFFERENT STATES OF ACTIVITY. 
A After a period of rest, in which case the outlines of the cells are indistinct, and the 
inner zone, i. e., the part of the cells (a) next the lumen ( c), is broad and filled with 
fine granules. B. After the gland has poured out its secretion, when the cell out¬ 
lines (d) are clearer, the granular zone ( a) is smaller, and the clear outer zone is wider. 
—From Yeo's Text-Book 0/Physiology , after Kiihne and Lea. 

The pancreas is similar in structure to the salivary glands, consisting of 
a system of ducts terminating in acini. The acini are tubular or flask- 
shaped, and consist of a basement membrane lined by a layer of cylindrical, 
conical cells, which encroach upon the lumen of the acini. The cells 
exhibit a difference in their structure (Fig. 4), and may be said to consist 
of two zones, viz., an outer parietal zone, which is transparent and appar¬ 
ently homogeneous, staining rapidly with carmine; an inner zone, which 
borders the lumen, and is distinctly granular and stains but slightly with 
carmine. These cells undergo changes similar to those exhibited by the 
cells of the salivary glands during and after active secretion. As soon as 





DIGESTION. 


35 


the secretory activity of the pancreas is established, the'granules disappear, 
and the inner granular layer becomes reduced to a very narrow border 
while the outer zone increases in size and occupies nearly the entire cell. 
During the intervals of secretion, however, the granular layer reappears 
and increases in size until the outer zone is reduced to a minimum. It 
would seem that the granular matter is formed by the nutritive processes 
occurring in the gland during rest, and is discharged during secretory 
activity into the ducts and takes part in the formation of the pancreatic 
secretion. 

The pancreatic juice is transparent, colorless, strongly alkaline and viscid, 
and has a specific gravity of 1.040. It is one of the most important of the 
digestive fluids, as it exerts a transforming influence upon all the classes of 
alimentary principles, and has been shown to contain at least three distinct 
ferments. It has the following composition :— 

COMPOSITION OF PANCREATIC JUICE. 


Water,.900.76 

Albuminoid substances,.90.44 

Inorganic salts,. 8.80 


1000 00 

The pancreatic juice is characterized by its action : 1st. Upon starch. 
When starch is subjected to the action of the juice, it is at once transformed 
into glucose; the change takes place more rapidly than when saliva is 
added. This action is caused by the presence of a special ferment, amyl- 
opsin. 2d. Upon albumin. The albuminous bodies are changed by the 
juice into, first, an alkali albumin, and then into peptone. The albumin 
does not swell up, as is the case in gastric digestion, but is gradually cor¬ 
roded and dissolved. This change is due to the presence of the ferment, 
trypsin. Long-continued action of trypsin converts the peptones into two 
crystalline bodies, leucine and tyrosin. 3d. Upon fats. The most striking 
action of the pancreatic juice is the etnulsification of the fats or their sub¬ 
division into minute particles of microscopic size. This change takes place 
rapidly and depends upon the alkalinity of the fluid and the quantity of 
albumin present, combined with the intestinal movements. The neutral 
fats are also decomposed into their corresponding fatty acids and glycerine ; 
the acids thus set free unite with the alkaline bases present in the intestine 
and form soaps. This decomposition of the neutral fats is caused by the 
ferment, steapsin. 4th. Upon cane sugar the juice also exerts a special 
influence, converting it readily into glucose. 






36 


HUMAN PHYSIOLOGY. 


The total quantity of this fluid secreted in twenty-four hours has not 
been accurately determined; it varies from one to two pounds ; it is poured 
out most abundantly an hour after meals. 

The Bile has an important influence in the elaboration of the food and 
its preparation for absorption. It is a golden-brown, viscid fluid, having a 
neutral or alkaline reaction and a specific gravity of 1.020. 

COMPOSITION OF BILE. 

Water,... 

Sodium glycocholate, \ 

Sodium taurocholate, j ' .. 

Fat,. 

Cholesterine,. 

Mucus and coloring matter,. 

Salts,. 

1000.00 

The Biliary salts , sodium glycocholate and taurocholate, are character¬ 
istic ingredients, and are formed in the liver by the process of secretion, 
from materials furnished by the blood. It is probable that they are derived 
from the nitrogenized compounds, though the stages in the process are 
unknown. They are reabsorbed from the small intestine to play some 
ulterior part in nutrition. 

Cholesterine is a product of waste taken up by the blood from the nervous 
tissues and excreted by the liver. It crystallizes in the form of rhombic 
plates, which are quite transparent. When retained within the blood, it 
gives rise to the condition of cholester<z 7 nia , attended with severe nervous 
symptoms. It is given off in the faeces under the form of stercorine. 

The Coloring matters which give the tints to the bile are biliver din and 
bilirubin , and are probably derived from the coloring matter of the blood. 
Their presence in any fluid can be recognized by adding to it nitric acid 
containing nitrous acid, when a play of colors is observed, beginning with 
green, blue, violet, red and yellow. 

The Bile is both a secretion and an excretion; it is constantly being 
formed and discharged by the hepatic ducts into the gall bladder, in which 
it is stored up, during the intervals of digestion. As soon as food enters 
the intestines, it is poured out abundantly, by the contraction of the walls 
of the gall bladder. 

The Amount secreted in 24 hours is about 2pounds. 

Functions of the Bile, (i) It assists in the emulsification of the fats 
and promotes their absorption. (2) It tends to prevent putrefactive changes 


859.2 

91.4 

9.2 

2.6 

29.8 

7.8 









ABSORPTION. 37 

in the food. (3) It stimulates the secretions of the intestinal glands, and 
excites the normal peristaltic movement of the bowels. 

The digested food, the chyme , is a grayish, pultaceous mass, but as it 
passes through the intestines it becomes yellow, from admixture with the 
bile. It is propelled onward by vermicular motion; by the contraction of 
the circular and longitudinal muscular fibres. 

As the digested food passes through the intestines, the nutritious mat¬ 
ters are absorbed into the blood, and the residue enters the large intestine. 

The Faeces consist chiefly of indigestible matters, ex cretin, slercorin 
and salts; varying in amount from 4 to 7 ozs. in 24 hours. 

Defecation is the voluntary act of extruding the faeces from the body; 
accomplished by a relaxation of the sphincter muscle, the contraction of the 
walls of the rectum, assisted by the abdominal muscles. 

The Gases contained in the stomach and small intestine are oxygen, 
nitrogen, hydrogen and carbonic acid. In the large intestine, carbonic 
acid, sulphuretted and carburetted hydrogen. They are introduced with 
the food, and also developed by chemical changes in the alimentary canal. 
They distend the intestines, aid capillary circulation, and tend to prevent 
pressure. 


ABSORPTION. 

The term absorption is applied to the passage or transference of material 
into the blood from the tissues, from the serous cavities, and from the 
mucous surfaces of the body. The most important of these surfaces, espe¬ 
cially in its relation to the formation of the blood, is the mucous surface of 
the alimentary canal; for it is from this organ that new materials are de¬ 
rived which maintain the quality and quantity of the blood. The absorp¬ 
tion of materials from the interstices of the tissues is to be regarded rather 
as a return to the blood of liquid nutritive material which has escaped from 
the blood vessels for nutritive purposes, and which, if not returned, would 
lead to an accumulation of such fluid and the development of dropsical 
conditions. 

The anatomical mechanisms involved in the absorptive process are 
primarily, the lymph spaces , the lymph capillaries and blood capillaries; 
secondarily, the lymphatic vessels and larger blood vessels. 

Lymph spaces, Lymph capillaries, Blood capillaries. Every¬ 
where throughout the body, in the intervals of connective tissue bundles, and 
in the interstices of the several structures of which an organ is composed, 


38 


HUMAN PHYSIOLOGY. 


are found spaces of irregular shape and size, determined largely by the nature 
of the organ in which they are found, which have been termed lymph, spaces 
or lacuna, from the fact that during the living condition they are continu¬ 
ally receiving the lymph which has escaped from the blood vessels through¬ 
out the body. In addition to the connective tissue lymph spaces, various 
observers have described special lymph spaces in the testicle, kidney, liver, 
thymus gland, and spleen; in all secreting glands between the basement 
membrane and blood vessels; around blood vessels (perivascular spaces) 
and around nerves. The serous cavities ot the body, peritoneal, pleural, 
pericardial, etc., may also be regarded as lymph spaces, which are in direct 
communication by open mouths or stomata with the lymphatic capillaries. 
This method of communication is not only true of serous membranes, but 
to some extent also of mucous membranes. The cylindrical sheaths and 
endothelial cells surrounding the brain, spinal cord and nerves, can also be 
looked upon as lymph spaces in connection with lymph capillaries. 

The lymphatic capillaries , in which the lymphatic vessels proper take 
their origin, are arranged in the form of plexuses of quite irregular shape. 
In most situations they are intimately interwoven with the blood vessels, 
from which, however, they can be readily distinguished by their larger 
calibre and irregular expansions. The wall of the lymph capillary is 
formed by a single layer of epithelioid cells, with sinuous outlines, and 
which accurately dovetail with each other. In no instance are valves 
found. In the villus of the small intestine the beginning of the lacteal is 
to be regarded as a lymph capillary, generally club-shaped, which at the 
base of the villus enters a true lymphatic; at this point a valve is present, 
which prevents regurgitation. The lymphatic capillaries anastomose freely 
with each other, and communicate on the one hand with the lymph spaces, 
and on the other with the lymphatic vessels proper. 

As the shape, size, etc., of both lymph spaces and capillaries are deter¬ 
mined largely by the nature of the tissues in which they are contained, it is 
not always possible to separate the one from the other. Their function, 
however, may be regarded as similar, viz:—the collection of the lymph 
which has escaped from the blood vessels, and its transmission onward into 
the .regular lymphatic vessels. 

The blood capillaries not only permit the escape of the liquid nutritive 
portions of the blood through their delicate walls, but are also engaged in 
the reabsorption of this transudate as well as in the absorption of new 
materials from the alimentary canal. The extensive capillary network 
which is formed by the ultimate subdivision of the arterioles in the sub¬ 
mucous tissue and villi of the small intestine forms an anatomical arrange- 


ABSORPTION. 


39 


ment well adapted for absorption. It is now well known that in the 
absorption of the products of digestion the blood capillaries are more active 
than the lymphatic capillaries. 

Lymphatic Vessels. The lymphatic vessels constitute a system of 
minute, delicate,transparent vessels, found in nearly all the organs and tissues 
of the body. Having their origin at the periphery in the lymphatic capil¬ 
laries and spaces, they gradually converge toward the trunk of the body and 
empty into the thoracic duct. In their course they pass through numerous 
small ovoid bodies, the lymphatic glands. 

The lymphatic vessels of the small intestine (the lacteals ) arise within 
the villous processes which project from the inner surface of the intestine 
throughout its entire extent. The wall of the villus is formed by an eleva¬ 
tion of the basement membrane, and covered by a layer of columnar epi¬ 
thelial cells. The basis of the villus consists of adenoid tissue, fine plexus 
of blood vessels, unstriped muscular fibres and the lacteal vessel. The 
adenoid tissue consists of a number of intercommunicating spaces, con¬ 
taining leucocytes. The lacteal vessel possesses a thin, but distinct wall, 
composed of endothelial plates, with here and there openings, which bring 
the interior of the villus into communication with the spaces of the adenoid 
tissue. 

The structure of the larger vessels resembles that of the veins, consisting 
of three coats.— 

I. External , composed of fibrous tissue and muscular fibres, arranged 
longitudinally. 2. Middle , consisting of white fibrous and yellow elastic 
tissue, non-striated muscular fibres, arranged transversely. 3. Internal , 
composed of an elastic membrane, lined by endothelial cells. 

Throughout their course are found numerous semilunar valves , looking 
toward the larger vessels, formed by a folding of the inner coat and 
strengthened by connective tissue. 

Lymphatic Glands. The lymphatic glands consist of an external 
capsule composed of fibrous tissue which contains non-striped muscular 
fibres: from its inner surface septa of fibrous tissue pass inward and sub¬ 
divide the gland substance into a series of compartments which communi¬ 
cate with each other. The blood vessels which penetrate the gland are 
surrounded by fine threads, forming a follicular arrangement, the meshes of 
which contain numerous lymph corpuscles. Between the follicular threads 
and the wall of the gland lies a lymph channel traversed by a reticulum of 
adenoid tissue. The lymphatic vessels after penetrating this capsule pour 
their lymph into this channel, through which it passes; it is then collected 


40 


HUMAN PHYSIOLOGY. 


Fig. 5. 



DIAGRAM SHOWING THE COURSE OF THE MAIN TRUNKS OF THE ABSORBENT SYSTEM. 

The lymphatics of lower extremities (D) meet the lacteals of intestines (LAC) at the 
receptaculum chyli (R C), where the thoracic duct begins. The superficial vessels 
are shown in the diagram on the right arm and leg (S), and the deeper ones on the 
arm to the left (D). The glands are here and there shown in groups. The small 
right duct opens into the veins on the right side. The thoracic duct opens into the 
union of the great veins of the left side of the neck (T ).—From Yeo's Text-Book 0/ 
Physiology . 




ABSORPTION. 


41 


by the efferent vessels and transmitted onward. The lymph corpuscles 
which are washed out of the gland into the lymph stream are formed, most 
probably, by division of pre-existing cells. 

The Thoracic Duct is the general trunk of the lymphatic system, into 
which the vessels of the lower extremities, of the abdominal organs, of the 
left side of the head and left arm empty their contents. It is about twenty 
inches in length, arises in the abdomen, opposite the third lumbar vertebra, 
by a dilatation, the receptaculum chyli; ascends along the vertebral column 
to the seventh cervical vertebra, and terminates in the venous system at 
the junction of the internal jugular and subclavian veins on the left side. 
The lymphatics of the right side of the head, of the right arm and the right 
side of the thorax, terminate in the right thoracic duct, about one inch in 
length, which joins the venous system at the junction of the internal jugular 
and subclavian on the right side. 

The general arrangement of the lymphatic vessels is shown in Fig. 5. 

The Blood Vessels which are concerned in the conduction of fresh 
nutritive material from the alimentary canal, have their origin in the elaborate 
capillary network in the mucous membrane. The small veins which emerge 
from this network gradually unite, forming larger and larger trunks which 
are known as the gastric, superior and inferior mesenteric veins. These 
finally unite to form the portal vein, a short trunk about three inches in 
length. The portal vein enters the liver at the transverse fissure, after 
which it forms a fine capillary plexus ramifying throughout the substance 
of the liver; from this plexus the hepatic veins take their origin, which 
finally empty the blood into the vena cava inferior. (See Fig. 6.) 

Absorption of Food. Physiological experiments have demonstrated 
that the agents concerned in the absorption of new materials from the ali¬ 
mentary canal are:—1st. The blood vessels of the entire canal, but more 
particularly those uniting to form the portal vein. 2d. The lymphatics 
coming from the small intestine which converge to empty into the thoracic 
duct. As a result of the action of the digestive fluids upon the different 
classes of food stuffs, albumins, sugars, starches and fats, there are formed, 
peptones, glucose and fatty emulsion , which differ from the former, in being 
highly diffusible, a condition essential to their absorption. In order that 
these substances may get into the blood, they must pass through the layer of 
cylindrical epithelial cells and the underlying basement membrane and into 
the lymph spaces of the villi and sub-mucous tissue. The mechanism by 
which the cells effect this passage of the food is but imperfectly understood. 

D 


42 


HUMAN PHYSIOLOGY. 


Osmosis and filtration are conditions, however, made use of by the cells in 
the absorptive process. 

The Products of digestion find their way into the general circulation by 
two routes:— 

I. The water,peptones, glucose and soluble salts, after passing into the 
lymph spaces of the villi, pass through the wall of the capillary blood vessel; 
entering the blood, they are carried to the liver by the vessels uniting to 


Fig. 6. 



Diagram of the portal vein {j>v) arising in the alimentary tract and spleen (*), and car¬ 
rying the blood from these organs to the liver .—From Yeo's Text-Book of Physiology. 

form the portal vein; emerging from the liver, they are emptied into the 
inferior vena cava by the hepatic vein. 

2. The emulsified fat enters the lymph capillary in the interior of the 
villus; by the contraction of the layer of muscular fibres surrounding it 
its contents are forced onward into the lymphatic vessel or lacteal; thence 























ABSORPTION. 43 

into the thoracic duct, and finally into the circulation at the junction of the 
internal jugular and subclavian veins on the left side. 

Absorption of Lymph. Similar to the absorption of food from the 
alimentary canal, is the absorption of lymph from the lymph spaces of the 
organs and tissues. During the passage of the blood through the capillary 
blood vessels, a portion of the liquor sanguinis or plasma or lymph, passes 
through the capillary wall out into the lymph spaces. The tissue cells are 
thus bathed with this new material; from it those substances are selected 
which are necessary for their growth, repair, and all purposes of nutrition. 
An excess of nutritive material, far beyond the needs of the tissues, transudes 
from the blood vessels, and it is this excess which is absorbed by the lym¬ 
phatics, and returned to the blood by the thoracic duct. It is quite probable 
also that a portion of this transudate is reabsorbed by the blood vessels. 

Properties and Composition of Lymph and Chyle. Lymph as 
found in the lymphatic vessels of animals, is a clear, colorless or opalescent 
fluid, having an alkaline reaction, a saline taste, and a specific gravity of 
about 1.040. It holds in suspension a number of corpuscles, resembling in 
their general appearance the white corpuscles of the blood. Their number 
has been estimated at 8200 per cubic millimetre, though the number varies 
in different portions of the lymphatic system. As the lymph flows through 
the lymphatic gland, it receives a large addition of corpuscles. Lymph 
corpuscles are granular in structure, and measure ^^th of an inch in 
diameter. When withdrawn from the vessels, lymph undergoes a spon¬ 
taneous coagulation, similar to that of the blood, after which it separates in 
serum and clot. 

COMPOSITION OF LYMPH. 


Water,.96*536 

Proteids (serum-albumin, fibrin-globulin),. 1.320 

Extractives (urea, sugar, cholesterine),. 1-559 

Fatty matters,.a trace. 

Salts,. 0.585 


100.000 

Chyle. Chyle is the fluid found in the lymphatic vessels, coming from 
the small intestine after the digestion of a meal containing fat. In the 
intervals of digestion, the fluid of these lymphatics is identical in all respects 
with the lymph found in all other regions of the body. As soon as 
the emulsified fat passes into the lymphatic vessels, and mingles with the 
lymph, it becomes milky in color, and the vessels which previously were 
invisible, become visible, and resemble white threads running between the 








44 


HUMAN PHYSIOLOGY. 


layers of the mesentery. Chyle has a composition similar to that of lymph, 
but it contains in addition, numerous fatty granules, each surrounded by an 
albuminous envelope. When examined microscopically, the chyle presents 
a fine molecular basis, made up of the finely divided granules of fat. 


COMPOSITION OF CHYLE. 

Water,. 

Albumin,. 

Fibrin,. 

Extractives,. 

Fatty matters,. 

Salts. 


902.37 

35-16 

3-70 

15.65 

36.01 

7.11 


1000.00 

Forces aiding the movement of Lymph and Chyle. The lymph and 
chyle are continually moving in a progressive manner, from the periphery or 
beginning of the lymphatic system, to the final termination of the thoracic 
duct. The force which primarily determines the movement of the lymph, 
has its origin in the beginnings of the lymphatic vessels, and depends upon 
the difference in pressure here and the pressure in the thoracic duct. The 
greater the quantity of fluid poured into the lymph spaces, the greater will 
be the pressure and consequently the movement. The. first movement of 
chyle is the result of a contraction of the muscular fibres within the walls 
of the villus. At the time of contraction, the lymphatic capillary is com¬ 
pressed and shortened, and its contents forced onward into the true lym¬ 
phatic. When the muscular fibres relax, regurgitation is prevented by the 
closure of the valve in the lymphatic at the base of the villus. 

As the walls of the lymphatic vessels contain muscular fibres, when they 
become distended, these fibres contract and assist materially in the onward 
movement of the fluid. 

The contraction of the general muscular masses in all parts of the body, 
by exerting an intermittent pressure upon the lymphatics, also hastens the 
current onward; regurgitation is prevented by the closure of valves which 
everywhere line the interior of the vessels. 

The respiratory movements aid the general flow of both lymph and chyle 
from the thoracic duct into the venous blood. During the time of an inspi¬ 
ratory movement, the pressure within the thorax, but outside the lungs, 
undergoes a diminution in proportion to the extent of the movement; as a 
result, the fluid in the thoracic duct outside of the thorax, being under a 
higher pressure, flows more rapidly into the venous system. At the time 
of an expiration, the pressure rises and the flow is temporarily impeded, 
only to begin again at the next inspiration. 









BLOOD. 


45 


BLOOD. 

The Blood is a nutritive fluid containing all the elements necessary for 
the repair of the tissues; it also contains principles of waste absorbed from 
the tissues, which are conveyed to the various excretory organs and by them 
eliminated from the body. 

The total amount of blood in the body is estimated to be about one-eighth 
of the body weight; from 16 to 18 pounds in an individual of average physi¬ 
cal development. The quantity varies during the 24 hours; the maximum 
being reached in the afternoon, the minimum in the early morning hours. 

Blood is a heterogeneous, opaque red fluid, having an alkaline reaction, 
a saline taste, and a specific gravity of 1.055. 

The opacity is due to the refraction of the rays of light by the elements 
of which the blood is composed. The color varies in hue, from a bright 
scarlet in the arteries to a deep purple in the veins, due to the presence of 
a coloring matter, kcemoglobin , in different degrees of oxidation. 

The alkalinity is constant, and depends upon the presence of the alka¬ 
line sodium phosphate, Na 2 HP 0 4 . 

The saline taste is due to the amount of sodium chloride present. 

The specific gravity ranges within the limits of health, from 1.045 t0 I -° 75 - 

The odor of the blood is characteristic, and varies with the animal from 
which it is drawn, due to the presence of caproic acid. 

The te?nperature of the blood ranges from 98° Fahr. at the surface to 
107° Fahr. in the hepatic vein; it loses heat by radiation and evaporation 
as it approaches the extremities, and as it passes through the lungs. 

Blood consists of two portions : 

1. The Liquor Sanguinis or Plasma , a transparent, colorless fluid, in 
which are floating— 

2. Red and white corpuscles; these constituting by weight less than one- 
half, 40 per cent., of the entire amount of blood. 

COMPOSITION OF PLASMA. 


DALTON. 

Water, . 902.00 

Albumin, . 53 -°° 

Paraglobulin,.22.00 

Fibrinogen, . 3.00 

Fatty matters,. 2.50 

Crystallizable nitrogenous matters,. 4.00 

Other organic matter,. 5 00 

Mineral salts,. 8.50 


1000.00 











46 


HUMAN PHYSIOLOGY. 


Water acts as a solvent for the inorganic matters and holds in suspension 
the corpuscular elements. 

Albumin is the nutritious principle of the blood; it is absorbed by the 
tissues to repair their waste and is transformed into the organic basis 
characteristic of each structure. 

Paraglobulin or jibrinoplastin is a soft amorphous substance precipitated 
by sodium chloride in excess, or by passing a stream of carbonic acid 
through dilute serum. 

Fibrinogen can also be obtained by strongly diluting the serum and 
passing carbonic acid through it for a long time, when it is precipitated as 
a viscous deposit. 

Fatty matter exists in small proportion, except in pathological conditions 
and after the ingestion of food rich in oleaginous matters; it soon disap¬ 
pears, undergoing oxidation, generating heat and force, or is deposited as 
adipose tissue. 

Sugar is represented by glucose, a product of the digestion of saccharine 
matter and starches in the alimentary canal; glycogenic matter is derived 
from the liver. 

The Saline constituents aid the process of osmosis, give alkalinity to 
the blood, promote the absorption of carbonic acid from the tissues into 
the blood, and hold other substances in solution; the most important 
are the sodium and potassium chlorides, the calcium and magnesium 
phosphates. 

Excrementitious matters are represented by carbonic acid, urea, creatin, 
creatinin, urates, oxalates, etc.; they are absorbed from the tissues by the 
blood and conveyed to the excretory organs, lungs, kidneys, etc. 

Gases. Oxygen, nitrogen and carbonic acid exist in varying proportions. 

BLOOD CORPUSCLES. 

The corpuscular elements of the blood occur under two distinct forms, 
which, from their color, are known as the red and white corpuscles. 

The Red Corpuscles , as they float in a thin layer of the Liquor 
Sanguinis, are of a pale straw color; it is only when aggregated in 
masses that they assume the bright red color. In form they are circu¬ 
lar and biconcave; they have an average diameter of the of 

an inch. 

In mammals, birds, reptiles, amphibia and fish the corpuscles vary in 
size and number, gradually becoming larger and less numerous as the scale 
of animal life is descended, e.g. :— 


BLOOD. 


47 


TABLE SHOWING COMPARATIVE DIAMETER OF RED 
CORPUSCLES. 

Mammals. Birds. Reptiles. Amphibia. Fish. 

Man, Eagle, Wr*. Turtle, T 5 \j T . Frog, T tW Perch, 

Chimpanzee, . Owl, 17 ' 53 . Tortoise, Toad, T u?3- Carp, 

Ourang, 3g 1 g3 . Sparrow, 3T W Lizard, xinnr- Proteus, Pike, 50 W 

Dog, ssW Swallow, 3T33 . Viper, IS V*. Siren, *£5- Eel, X7is- 

Cat, nW* Pigeon, xsVa* Amphiuma, 5^5. 

*Jog, Turkey, 33 ' ?3 . 

Horse, ?bW* Goose, rgSB* 

Ox, 35B7' Swan, xbW 


In man and the mammals the red corpuscles present neither a nucleus 
nor a cell wall, and are universally of a small size. They can be readily 
distinguished from the corpuscles of birds, reptiles and fish, in which they 
are larger, oval in shape and possess a well-defined nucleus. 

The red corpuscles are exceedingly numerous, amounting to about 
5,000,000 in a cubic millimetre of blood. In structure they consist of a 
firm, elastic, colorless framework, the stroma , in the meshes of which is 
entangled the coloring matter, the hemoglobin. 


CHEMICAL COMPOSITION OF RED CORPUSCLES. 


Water,.688.00 

Globulin,.282.22 

Haemoglobin,. 16.75 

Fatty matter,. 2.31 

Extractives,. 2.60 

Mineral salts,. 8.12 


1000.00 

Hemoglobin , the coloring matter of the corpuscles, is an albuminous 
compound, composed of C. O. H. N. S. and iron. It may exist either in 
an amorphous or crystalline form. When deprived of all its oxygen, 
except the quantity entering into its intimate composition, the haemoglobin 
becomes dark in color, somewhat purple in hue, and is known as reduced 
hemoglobin. When exposed to the action of oxygen, it again absorbs a 
definite amount and becomes scarlet in color, and is known as oxy-hemo- 
globin. The amount of oxygen absorbed is 1.76 c.cm. cubic inch) for 
1 milligramme grain) of haemoglobin. 

It is this substance which gives the color to the venous and arterial 
blood. As the venous blood passes through the capillaries of the lungs, 
the reduced hemoglobin absorbs the oxygen from the pulmonary air and 
becomes oxy-hemoglobin y scarlet in color, and the blood becomes arterial. 
When the arterial blood passes into the systemic capillaries, the oxygen 









48 


HUMAN PHYSIOLOGY. 


is absorbed by the tissues, the haemoglobin becomes reduced, purple in 
color, and the blood becomes venous. A dilute solution of oxy-haemo- 
globin gives two absorption bands between the lines D and E of the 
solar spectrum. Reduced haemoglobin gives but one absorption band, 
occupying the space existing between the two bands of the oxy-haemo- 
globin spectrum. 

The Function of the red corpuscle is, therefore, to absorb oxygen and 
carry it to the tissues; the smaller the corpuscles and the greater the 
number, the greater is the quantity of oxygen absorbed ; and, consequently, 
all the vital functions of the body become more active. 

The White Corpuscles are far less numerous than the red, the proportion 
being, on an average, about i white to 350 or 400 red; they are globular 
in shape, and measure the °f an inch i n diameter, and consist of a 
soft, granular, colorless substance, containing several nuclei. 

The white corpuscles possess the power of spontaneous movement, alter¬ 
nately contracting and expanding, throwing out processes of their substance' 
and quickly withdrawing them, thus changing their shape from moment 
to moment. These movements resemble those of the amoeba, and for this 
reason are termed amoeboid. They also possess the capability of moving 
from place to place. In the interior of the vessels they adhere to the inner 
surface, while the red corpuscles move through the centre of the stream. 

The white corpuscles are identical with the leucocytes, and are found 
in milk, lymph, chyle and other fluids. 

Origin of Corpuscles. The red corpuscles take their origin from the 
mesoblastic cells in the vascular area of the developing embryo. 

In the adult they are produced from colorless nucleated corpuscles 
resembling the white corpuscles. The spleen is the organ in which they 
are finally destroyed. 

The white corpuscles originate from the leucocytes of the adenoid tissue, 
and subsequently give rise to the red corpuscles and partly to new tissues 
that result from inflammatory action. 


COAGULATION OF THE BLOOD. 

When blood is withdrawn from the body and allowed to remain at rest, 
it becomes somewhat thick and viscid in from three to five minutes; this 
viscidity gradually increases until the entire volume of blood assumes a 
jelly-like consistence, which occupies from five to fifteen minutes. 

As soon as coagulation is completed, a second process begins, which 
consists in the contraction of the coagulum and the oozing of a clear, straw- 


BLOOD. 


49 


colored liquid, the serum , which gradually increases in quantity as the clot 
diminishes in size, by contraction, until the separation is completed, which 
occupies from 12 to 24 hours. 

The changes in the blood are as follows:— 

Before coagulation. 


f Liq. Sanguinis 


Living blood. -{ Plasma. 


Consisting of 


[ Corpuscles. Red and white. 

After coagulation. 

f Crassamentum. ) ^ . . . 

I Clot or coagulum. } Contamm g 
Dead blood. -{ 

I Serum. Containing 


C Water, 
j Albumin. 

] Fibrinogen. 
[ Salts. 


{ 


Fibrin. 

Corpuscles. 

Water. 

Albumin. 

Salts. 


The serum, therefore, differs from the Liquor Sanguinis in not containing 
fibrin. 

In from 12 to 24 hours the upper surface of the clot presents a grayish 
appearance, the buffy coat, which is due to the rapid sinking of the red 
corpuscles beneath the surface, permitting the fibrin to coagulate without 
them, which then assumes a grayish yellow tint. Inasmuch as the white 
corpuscles possess a lighter specific gravity than the red, they do not sink 
so rapidly, and becoming entangled in the fibrin, assist in forming the buffy 
coat. Continued contraction gives a cupped appearance to the surface of 
the clot. 

Inflammatory states of the blood produce a marked increase in the 
buffed and cupped condition, on account of the aggregation of the cor¬ 
puscles, and their tendency to rapid sinking. 

Nature of Coagulation. Coagulated fibrin does not preexist in the 
blood, but is formed at the moment blood is withdrawn from the vessels. 
According to Denis, a liquid substance, plasmine , exists in the blood, 
which, when withdrawn from the circulation, decomposes into fibrin and 
met-albumin. 

According to Schmidt, fibrin results from the union of fibrinoplastin 
(paraglobulin) and fibrinogen , brought about by the presence of a third 
substance, the fibrin ferment. 

According to Hammersten and others, the fibrin obtained from the blood 
after coagulation, comes from the fibrinogen alone, the conversion being 
brought about by the presence of a ferment substance, paraglobulin in this 


50 


HUMAN PHYSIOLOGY. 


case having nothing to do with the change. This view is supported by the 
fact that the quantity of fibrin obtained from the blood is never greater than 
the quantity of fibrinogen previously present. The origin of the ferment is 
obscure, but there is reason to believe that it comes from the injured vascu¬ 
lar coats or from the breaking of the white corpuscles. 

Conditions Influencing Coagulation. The process is retarded by 
cold, retention within living vessels, neutral salts in excess, inflammatory 
conditions of the system, imperfect aeration, exclusion from air, etc. 

It is hastened by a temperature of ioo° F., contact with air, rough sur¬ 
faces and rest. 

Blood coagulates in the body after the arrest of the circulation in the 
course of 12 to 24 hours; local arrest of the circulation, from compression 
or a ligature, will cause coagulation, thus preventing hemorrhages from 
wounded vessels. 

The Composition of the Blood varies in different portions of the body. 
The arterial differs from the venous , in being more coagulable, in contain¬ 
ing more oxygen and less carbonic acid, in having a bright scarlet color, 
from the union of oxygen with haemoglobin; the purple hue of venous blood 
results from the deoxidation of the coloring matter. 

The blood of the portal vein differs in constitution, according to different 
stages of the digestive process; during digestion it is richer in water, 
albuminous matter and sugar; occasionally it contains fat; corpuscles are 
diminished, and there is an absence of biliary substances. 

The blood of the hepatic vein contains a larger proportion of red and 
white corpuscles; the sugar is augmented, while albumin, fat and fibrin 
are diminished. 

Pathological conditions of the blood. 

1. Plethora —increase in the volume or quantity of blood. 

2. Ancemia —deficiency of red globules with increase of water. 

3. Leucocythemia —increase of white and diminution of red corpuscles. 

4. Glycohcemia —excess of sugar in the blood. 

5. Uroemia —increase in the amount of urea. 

6. Cholestercemia —an excess of cholesterine in the blood. 

7. Thrombosis and embolism —clotting of blood in the vessels and 
dissemination of coagula. 

8. Lipcemia —an excess of fat. 

9. Melancemia —pigment in the blood. 


CIRCULATION OF THE BLOOD. 


51 


CIRCULATION OF THE BLOOD. 

The Circulatory Apparatus by which the blood is* distributed to all 
portions of the body consists of a central organ, the heart, with which is 
connected a system of closed vessels, known as arteries, capillaries and veins. 
Within this system the blood is kept, by the action of the heart, in continual 
movement, distributing nutritious matter to all portions of the body and 
carrying waste matters from the tissues to the various eliminating organs. 

The heart is a hollow muscular organ, pyramidal in shape, measuring 
about 5)4 inches in length, about 3^ in breadth, weighing from 10-12 oz. 
in the male and from 8-10 oz. in the female. Situated in the thoracic 
cavity, between the lungs, its base is directed upward, backward and to the 
right, its apex is directed downward and to the left. 

Pericardium. The heart is surrounded by a closed fibrous membrane 
called the pericardium. The inner surface of this membrane is lined by a 
serous membrane, which is also reflected over the surface of the heart; 
between the two surfaces of the serous membrane is found a small quantity 
of fluid, the pericardial fluid, which lubricates the surfaces and prevents 
friction during the movements of the heart. The interior of the heart is also 
lined by a serous membrane called the endo-cardium. 

Cavities of the Heart. The general cavity of the heart is subdivided 
by a longitudinal septum into a right and left half; each of these cavities is 
in turn subdivided by a transverse constriction into two smaller cavities 
which communicate with each other and are known as the auricles and 
ventricles. The orifice between the auricle and ventricle being known as 
the auricula-ventricular orifice. The heart therefore consists of four 
cavities, a right auricle and ventricle and a left auricle and ventricle. 

Into the right auricle, the two terminal trunks of the venous system, the 
superior and inferior vence cavce , empty the venous blood which has been 
collected from all parts of the system; from the right ventricle arises the 
pulmonary artery which passing into the lungs, distributes the blood to the 
walls of the air cells of the lungs; into the left auricle empty four pulmonary 
veins which have collected the blood from the lung capillaries; from the 
left ventricle springs the aorta, the general trunk of the arterial system 
whose branches distribute the blood to the entire system. 

The Valves of the Heart. The valves of the heart are formed by a 
reduplication of the endocardium strengthened by connective tissue. At the 
auriculo-ventricular openings on the right and left sides of the heart respec¬ 
tively are found the tricuspid and mitral valves. The tricuspid valve 


52 


HUMAN PHYSIOLOGY. 


consists of three, the mitral of two cusps or segments which project into 
the interior of the ventricle when it does not contain blood. At their bases 
the segments are^united so as to form an annular membrane attached to the 
margin of the orifice. To the free edges of the valves are attached numerous 
fine threads, the chorda tendinece which are the tendons of the small papillary 
muscles springing from the walls of the ventricles. 

The Semilunar Valves. At the openings of the pulmonary artery and 
the aorta are found three cupped-shaped or semilunar valves, the free edges 
of which are directed away from the interior of the heart. The anatomical 
arrangement of the valves is such that upon their closure regurgitation of 
the blood is prevented. 

Movement of the Blood. The blood within the vascular apparatus is 
in continual movement from the left side of the heart through the arterial sys¬ 
tem, capillaries and veins to the right side, and from the right side through 
the pulmonary artery, capillaries and veins to the original point of departure. 
The cause of this movement is the difference of pressure which exists 
between the blood within the aorta and the terminations of the venae cavae, 
and between the blood of the pulmonary artery and the pulmonary veins. 

The function of the heart is to propel the blood through the blood-ves¬ 
sels, which it does by raising or maintaining this higher pressure in the 
aorta and pulmonary artery. This is accomplished by alternate contrac¬ 
tions and relaxations of its muscular walls. These two movements are 
known respectively as the systole and the diastole. 

Course of the Blood through the Heart. The venous blood re¬ 
turned to the heart by the superior and inferior venae cavae is emptied during 
the diastole into the right auricle, in the contraction of which it is forced 
through the right auriculo-ventricular opening into the right ventricle and 
distends it. Upon the contraction of the ventricle the blood is propelled 
through the pulmonary artery into the lungs, where it undergoes aeration 
and is changed in color. 

The arterial blood is now collected by the pulmonary veins and poured 
into the left auricle; thence it passes into the left ventricle, which becomes 
fully distended. Upon the contraction of the ventricle, the blood is pro¬ 
pelled into the aorta, and by it distributed to the system at large, to be again 
returned to the heart by the veins. 

Regurgitation from the ventricles into the auricles during the systole is 
prevented by the closure of the tricuspid and mitral valves; regurgitation 
from the pulmonary artery and aorta into the ventricles during the diastole 
is prevented by the closure of the semilunar valves. 


CIRCULATION OF THE BLOOD. 


53 


While there is but one circulation physiologists frequently divide the cir¬ 
culatory apparatus into:— 

1. The Systemic Circulation , which includes the movement of the blood 
from the left side of the heart through the 
aorta and its branches, through the capilla¬ 
ries and veins to the right side. 

2. The Pulmonary Circulation , which 
includes the course of the blood from the 
right side through the pulmonary artery, 
through the capillaries of the lungs and 
pulmonary veins to the left side of the 
heart. 

3. The Portal Circulation , which in¬ 
cludes the portal vein. This is formed by 
the union of the radicles of the gastric, 
mesenteric and splenic veins, and carries 
the blood directly into the liver, where the 
vein again divides into a fine capillary 
plexus from which the hepatic veins arise 
which empty into the ascending venae cavae. 

Movements of the Heart. At each 
revolution, during the systole, the heart 
hardens and becomes shortened in its long 
diameter; its apex is raised up, rotated on 
its axis from left to right and thrown for¬ 
ward against the walls of the chest. The 
impulse of the heart, observed about two 
inches below the nipple, and one inch to 
the sternal side, between the fifth and sixth 
ribs, is caused mainly by the apex of the 
heart striking against the chest walls, as- a, right, b, left auricle ; A, right, B, 
sisted by the distention of the great vessels 2> aorta . a ’ r £ a of pulmonary, 

about the base of the heart. K - area of systemic circulation ; 

o, the superior vena cava; tj, area 

o j r ,, T t t T f 1 supplying the inferior vena cava, u; 

Sounds Of the Heart. If the ear be d, d, intestine ; m, mesenteric ar- 

placed over the cardiac region, two distinct hlZLl *’ 

sounds are heard during each revolution of 

the heart, closely following each other and which differ in character. 

The sound coinciding with the systole in point of time, the first sound , 
is long and dull, and caused by the closure and vibration of the auriculo- 



SCHEME OF THE CIRCULATION. 












54 


HUMAN PHYSIOLOGY. 


ventricular valves, the contraction of the walls of the ventricles and the 
apex beat; the second sound , occurring during the diastole , is short and 
sharp, and caused jiy the closure of the semilunar valves. 

The capacity of the left ventricle when jully distended is estimated at 
from four to seven ounces. 

The frequency of the heart’s action varies at different periods of life, 
but in the adult male it beats about 72 times per minute. It is influenced 
by age, exercise, posture, digestion, etc. 

Age. Before birth, the number of pulsations per minute averages 140 

During the first year it diminishes to,.128 

During the third year diminishes to,. 95 

From the eighth to the fourteenth year averages, .... 84 
In adult life the average is,.72 

Exercise and digestion increase the frequency of the heart’s action. 

Posture influences the number of pulsations per minute; in the male, 
standing, the average is 81; sitting, 71; lying, 66; independent, for the 
most part, of muscular effort. 

The Rhythmical movements of the heart are dependent upon—1. 
An inherent irritability of the muscular fibre, which manifests itself as long 
as the nutrition is maintained. 2. The continuous flow of blood through 
its cavities, distending them and stimulating the endocardium. 

The force exerted by the left ventricle at each contraction has been 
estimated at 52 pounds. If a tube be inserted into the aorta, the pressure 
there will be sufficient to support a column of blood nine feet or a column 
of mercury six inches in height, the weight in either case being about four 
pounds. The estimation of the force which the heart is required to exert 
to support this column of blood, is arrived at by multiplying the pressure 
in the aorta (4 pounds) by the area of the internal surface of the left 
ventricle (about 13 inches). Each .inch of the ventricle being capable of 
supporting a downward pressure of 4 pounds. 

Work done by the Heart. The work done by the heart is estimated 
by multiplying the amount of blood sent out from the right and left ventricles 
at each contraction, by the pressure in the pulmonary artery and aorta 
respectively, e. g., when the right ventricle contracts, it forces out one- 
quarter pound of blood, and in so doing must overcome a pressure in the 
pulmonary artery sufficient to support a column of blood three feet in 
height; that is, must exert energy sufficient to raise % lb. 3 feet, or X X3 
or ^ lb. one foot. When the left ventricle contracts, it sends out lb. of 
blood, and in so doing, the left ventricle must overcome a pressure in the 





CIRCULATION OF THE BLOOD. 


55 


aorta sufficient to support a column of blood nine feet in height; that is, 
must exert energy sufficient to raise X lb. 9 feet, or X X 9 or 2 X lbs. one 
foot. Work done is estimated by the amount of energy required to raise 
a definite weight a definite height, the unit, the foot pound, being that 
required to raise one pound one foot. 

The heart, therefore, at each systole exerts energy sufficient to raise 3 foot 
pounds, and as it contracts 72 times per minute, it would raise in that 
time 3 X 72 or 216 foot pounds; and in one hour 216 X 60or 12,960foot 
pounds; and in 24 hours 12,960 X 2 4 or 311,040 foot pounds or 138.5 
foot tons 

Influence of the Nervous System upon the Heart. When the 
heart of a frog is removed from the body, it continues to beat for a 
variable length of time, depending upon the nature of the conditions 
surrounding it. The heart of warm-blooded animals continues to beat 
but for a very short time. The cause of the continued pulsations of the 
frog heart is the presence of nervous ganglia in its substance. These 
ganglia have not been shown to exist in the mammalian heart, but 
there is reason to believe that the nervous mechanism is fundamentally 
the same. 

The ganglia of the heart are three in number, one situated at the opening 
of the inferior vena cava (the ganglion of Remak), a second situated 
in the auriculo-ventricular septum (the ganglion of Bidder), and a third 
situated in the inter-auricular septum (the ganglion of Ludwig). The first 
two are motor in function and excite the pulsations of the heart; the third 
is inhibitory in function and retards the action of the heart. The actions 
of these ganglia, though for the most part automatic, are modified by im¬ 
pressions coming through nerves from the medulla oblongata. When the 
inhibitory centre is stimulated by muscarin, the heart is arrested in diastole ; 
when atropia is applied, the heart recommences to beat, because atropia 
paralyzes the inhibitory centre. 

The nerves modifying the action of the heart are the Pneumogastric 
(Vagus) and the Accelerator nerves. 

The Pneumogastric nerve , after emerging from the medulla, receives 
motor fibres from the spinal accessory nerve. It then passes downward, 
giving off branches, some of which terminate in the inhibitory ganglion. 
Stimulation of the vagus by increasing the activity of the inhibitory centre 
arrests the heart in diastole with its cavities full of blood; but as the stimu¬ 
lation is only temporary, after a few seconds the heart recommences to 
beat; at first the pulsations are weak and feeble, but soon regain their 
original vigor. After the administration of atropia in sufficient doses to de- 


56 


HUMAN PHYSIOLOGY. 


stroy the termination of the pneumogastric, stimulation of its trunk has no 
effect upon the heart. The inhibitory fibres in the vagus are constantly 
in action, for division of the nerve on both sides is always followed by an 
increase in the frequency of the heart’s pulsations. 

The Acceleratorfibres arise in the medulla, pass down the cord, emerge 
in the cervical region, pass to the last cervical and first dorsal ganglia of the 
sympathetic, and thence to the heart. Stimulation of these fibres causes an 
increased frequency of the heart’s pulsations, but they are diminished in 
force. 


ARTERIES. 

The Arteries are a series of branching tubes conveying blood to all 
portions of the body. They are composed of three coats— 

1. External , formed of areolar and elastic tissue. 

2. Middle, contains both elastic and muscular fibres, arranged trans¬ 

versely to the long axis of the artery. The elastic tissue is more 
abundant in the larger vessels, the muscular in the smaller. 

3. Internal , composed of a thin homogeneous membrane, covered with 

a layer of elongated endothelial cells. 

The arteries possess both elasticity and contractility. 

The Property of Elasticity allows the arteries already full to accommo¬ 
date themselves to the incoming amount of blood, and to convert the 
intermittent acceleration of blood in the large vessels into a steady and 
continuous stream in the capillaries. 

The Contractility of the smaller vessels equalizes the current of blood, 
regulates the amount going to each part, and promotes the onward flow of 
blood. 

Blood Pressure. Under the influence of the ventricular systole, the 
recoil of the elastic walls of the arteries, and the resistance offered by the 
capillaries, the blood is constantly being subjected to a certain amount of 
pressure. If a large artery of an animal be divided, and a glass tube of 
the same calibre be inserted into its orifice, the blood will rise to a height 
of about nine feet; or if it be connected with a mercurial manometer, the 
mercury will rise to a height of six inches. This height will be a measure 
of the pressure in the vessel. The absolute quantity of mercury sustained 
by an artery can be arrived at by multiplying the height of the column by 
the area of a transverse section of that artery. 

The pressure of the blood is greatest in the large arteries, but gradually 
decreases toward the capillaries. 


ARTERIES. 


57 


The blood pressure is increased or diminished by influences acting upon 
the heart or upon the peripheral resistance of the capillaries, viz.:— 

If, while the force of the heart remains the same, the number of pulsa¬ 
tions per minute increases, thus increasing the volume of blood in the 
arteries, the pressure rises. If the rate remains the same, but the force 
increases, the pressure again rises. Causes that increase the peripheral 
resistance by contracting the arterioles, e. g ., vasomotor nerves, cold, etc., 
produce an increase of the pressure. 

On the other hand, influences which diminish either the volume of the 
blood, or the number of pulsations, or the force of the heart, or the peri¬ 
pheral resistance, lower the pressure. 

The Pulse is the sudden distention of the artery in a transverse and 
longitudinal direction, due to the injection of a volume of blood into the 
arteries at the time of the ventricular systole. As the vessels are already 
full of blood, they must expand in order to accommodate themselves to the 
incoming volume of blood. The blood pressure is thus increased, and the 
pressure originating at the ventricle excites a pulse wave , which passes 
from the heart toward the capillaries at the rate of about twenty-nine feet 
per second. It is this wave that is appreciated by the finger. 

The Velocity with which the blood flows in the arteries diminishes from 
the heart to the capillaries, owing to an increase of the united sectional area 
of the vessels, and increases in rapidity from the capillaries toward the 
heart. It moves most rapidly in the large vessels, and especially under 
the influence of the ventricular systole. From experiments on animals, 
it has been estimated to move in the carotid of man at the rate of sixteen 
inches per second, and in the large veins at the rate of four inches per 
second. 

The Calibre of the blood vessels is regulated by the vasomotor 
nerves, which have their origin in the gray matter of the medulla oblongata. 
They issue from the spinal cord through the anterior roots of spinal nerves, 
pass through the sympathetic ganglia, and ultimately are distributed to the 
coats of the blood vessels. They exert, at different times, a constricting and 
dilating action upon the vessels, thus keeping up the arterial tonus. 

Capillaries. The capillaries constitute a network of vessels of micro 
scopic size, which distribute the blood to the inmost recesses of the tissues, 
inosculating with the arteries on the one hand and the veins on the other; 
they branch and communicate in every possible direction. 

The diameter of a capillary vessel varies from the to the of 
an inch; their walls consist of a delicate homogeneous membrane, the 
E 


58 


HUMAN PHYSIOLOGY. 


an * n Sickness, lined by flattened, elongated, endothelial 
cells, between which, here and there, are observed stomata. 

It is through the agency of the capillary vessels that the phenomena ol 
nutrition and secretion takes place, for here the blood flows in an equable 
and continuous current, and is brought into intimate relationship with the 
tissues, two of the essential conditions for proper nutrition. 

The rate of movement in the capillary vessels is estimated at one inch 
in thirty seconds. 

In the capillary current the red corpuscles may be seen hurrying down 
the centre of the stream, while the white corpuscles in the still layer 
adhere to the walls of the vessel, and at times can be seen to pass through 
the walls of the vessel by amoeboid movements. 

The passage of the blood through the capillaries is mainly due to the 
force of the ventricular systole and the elasticity of the arteries; but it is 
probably also aided by a power resident in. the capillaries themselves, the 
result of a vital relation between the blood and the tissues. 

The Veins are the vessels which return the blood to the heart; they 
have their origin in the venous radicles, and as they approach the heart* 
converge to form larger trunks, and terminate finally in the venae cavae. 

They possess three coats— 

1. External , made up of areolar tissue. 

2. Middle , composed of non-striated muscular fibres, yellow, elastic and 
fibrous tissue. 

3. Internal , an endothelial membrane, similar to that of the arteries. 

Veins are distinguished by the possession of valves throughout their 

course, which are arranged in pairs, and formed by a reflection of the inter¬ 
nal coat, strengthened by fibrous tissues; they always look toward the heart,, 
and when closed prevent a return of blood in the veins. Valves are most 
numerous in the veins of the extremities, but are entirely absent in many 
others. 

The onward flow of blood in the veins is mainly due to the action of 
the heart; but is assisted by the contraction of the voluntary muscles and 
the force of respiration. 

Muscular contraction , which is intermittent, aids the flow of blood in 
the veins, by compressing them. As regurgitation is prevented by the 
closure of the valves, the blood is forced onward toward the heart. 

Rhythmical movements of veins have been observed in some of the lower 
animals, aiding the onward current of blood. 

During the movement of inspiration the thorax is enlarged in all its 


RESPIRATION. 


59 


diameters, and the pressure on its contents at once diminishes. Under 
these circumstances a suction force is exerted upon the great venous trunks, 
which causes the blood to flow with increased rapidity and volume toward 
the heart. 

Venous pressure. As the force of the heart is nearly expended in 
driving the blood through the capillaries, the pressure in the venous system 
is not very marked, not amounting in the jugular vein of a dog to more 
than that of the carotid artery. 

The time required for a complete circulation of the blood throughout the 
vascular system has been estimated to be from 20 to 30 seconds, while for 
the entire mass of blood to pass through the heart 58 pulsations would be 
required, occupying 48 seconds. 

The Forces keeping the blood in circulation are— 

1. Action of the heart. 

2. Elasticity of the arteries. 

3. Capillary force. 

4. Contraction of the voluntary muscles upon the veins. 

5. Respiratory movements. 


RESPIRATION. 

Respiration is the function by which Oxygen is absorbed into the 
blood and carbonic acid exhaled. The appropriation of the oxygen and 
the evolution of carbonic acid takes place in the tissues as a part of the 
general nutritive process; the blood and respiratory apparatus constituting 
the media by means of which the interchange of gases is accomplished. 

The Respiratory Apparatus consists of the larynx, trachea and lungs. 

The Larynx is composed of firm cartilages, united together by liga¬ 
ments and muscles; running antero-posteriorly across the upper opening are 
•four ligamentous bands, the two superior, or false vocal cords, and the two 
inferior, or true vocal cords, formed by folds of the mucous membrane. 
They are attached anteriorly to the thyroid cartilages and posteriorly to the 
arytenoid cartilages and are capable of being separated by the contraction 
of the posterior crico-arytenoid muscles, so as to admit the passage of air 
into and from the lungs. 

The Trachea is a tube from four to five inches in length, three-quarters 
of an inch in diameter, extending from the cricoid cartilage of the larynx 
to the third dorsal vertebra, where it divides into the right and left bronchi. 


60 


HUMAN PHYSIOLOGY. 


It is composed of a series of cartilaginous rings, which extend about two- 
thirds around its circumference, the posterior third being occupied by fibrous 
tissue and non-striated muscular fibres which are capable of diminishing its 
calibre. 

The trachea is covered externally by a tough, fibro-elastic membrane, 
and internally by mucous membrane, lined by columnar ciliated epithelial 
cells. The cilia are always waving from within outward. When the two 
bronchi enter the lungs they divide and subdivide into numerous and 
smaller branches, which penetrate the lung in every direction until they 
finally terminate in the pulmonary lobules. 

As the bronchial tubes become smaller their walls become thinner; the 
cartilaginous rings disappear, but are replaced by irregular angular plates 
of cartilage; when the tube becomes less than the zs of an inch in di¬ 
ameter they wholly disappear, and the fibrous and mucous coats blend 
together, forming a delicate, elastic membrane, with circular muscular fibres. 


Fig. 8. The Lungs occupy the cavity of the 

thorax, are conical in shape, of a pink 
color and a spongy texture. They are 
composed of a great number of distinct 
lobules, the pulmonary lobules , con¬ 
nected together by interlobular con¬ 
nective tissue. These lobules vary in 
size, are of an oblong shape, and are 
composed of the ultimate ramifications 
of the bronchial tubes, within which are 
contained the air vesicles or cells. The 
walls of the air vesicles, exceedingly 
thin and delicate, are lined internally by 
a layer of tessellated epithelium, exter¬ 
nally covered by elastic fibres, which 
give the lungs their elasticity and dis- 
tensibility. 

The Venous Blood is distributed to 
the lungs for aeration by the pulmonary 
artery, the terminal branches of which 
form a rich plexus of capillary vesssls 
surrounding the air cells; the air and 
blood are thus brought into intimate relationship, being separated only by 
the delicate walls of the air cells and capillaries. 



Diagram of the respiratory organs. 

The windpipe leading down from the 
larynx is seen to branch into two 
large bronchi, which subdivide after 
they enter their respective lungs. 




RESPIRATION. 


61 


The thoracic cavity in which the respiratory organs are lodged is of a 
conical shape, having its apex directed upward, its base downward. Its 
framework is formed posteriorly by the spinal column, anteriorly by the 
sternum, and laterally by the ribs and costal cartilages. Between and over 
the ribs lie muscles, fascia and skin; above the thorax is completely closed 
by the structures passing into it and by the cervical fascia and skin; below 
it is closed by the diaphragm. It is therefore an air-tight cavity. 

The Pleura. Each lung is surrounded by a closed serous membrane, 
the pleura, one layer of which, the visceral , is reflected over the lung, the 
other, the parietal , reflected over the wall of the thorax; between the two 
layers is a small amount of fluid which prevents friction during the play of 
the lungs in respiration. 

Owing to the elastic tissue which is present in the lungs, they are very 
readily distensible, so much so, indeed, that the pressure of the air inside 
the trachea and lungs is sufficient to distend them until they completely 
fill all parts of the thoracic cavity not occupied by the heart and great 
vessels. The elastic tissue endows them not only with distensibility, 
but also with the power of elastic recoil, by which they are enabled 
to accommodate themselves to all variations in the size of the thoracic 
cavity. 

When the chest walls recede, the air within the lungs expands and 
presses them against the ribs; when the chest walls contract, the air 
being driven out, the elastic tissue recoils and the lungs return to their 
original condition. The movements of the lungs are therefore entirely 
passive. 

As the capacity of the chest in a state of rest is greater than the volume 
of the lungs after they are collapsed, it is quite evident that in the living 
condition the lungs are distended and in a state of elastic tension, which 
is greater or less in proportion as the thoracic cavity is increased or dimin¬ 
ished in size. The elastic tissue, always on the stretch, is endeavoring to 
pull the visceral layer of the pleura away from the parietal layer, but is 
antagonized by the pressure of the air within the air passages. This con¬ 
dition of things persists as long as the thoracic cavity remains air tight; but 
if an opening be made in the thoracic wall, the pressure of the external air 
which was previously supported by the practically rigid walls of the thorax 
now presses upon the lung with as much force as the air within the lung. 
The two pressures being neutralized, there is nothing to prevent the elastic 
tissue from recoiling, driving the air out and collapsing. The elastic ten¬ 
sion of the lungs can be readily measured in man after death by inserting 


62 


HUMAN PHYSIOLOGY. 


a manometer into the trachea. Upon opening the thorax and allowing the 
tissue to recoil, the air presses upon the mercury and elevates it, the extent 
to which it is raised being the index of the pressure. Hutchinson calcu¬ 
lated the pressure to be one-half pound to the square inch of the lung 
surface. 

Respiratory movements. The movements of respiration are two, and 
consist of an alternate dilatation and contraction of the chest, known as 
inspiration and expiration. 

1. Inspiration is an active process, the result of the expansion of the 
thorax, whereby air is introduced into the lungs. 

2. Expiration is a partially passive process, the result of the recoil of 
the elastic walls of the thorax, and the recoil of the elastic tissue of the 
lungs, whereby the carbonic acid is expelled. 

In Inspiration the chest is enlarged by an increase in all its diameters 
viz.:— 

1. The vertical is increased by the contraction and descent of the dia¬ 
phragm when it approximates a straight line. 

2. The antero-posterior and transverse diameters are increased by the 
elvation and rotation of the ribs upon their axes. 

In ordinary tranquil inspiration the muscles which elevate the ribs and 
thrust the sternum forward, and so increase the diameters of the chest, are 
the external intercostals , running from above downward and forward, the 
sternal portion of the internal intercostals and the levatores costarum. 

In the extraordinary efforts of inspiration certain auxiliary muscles are 
brought into play, viz.: the sterno-mastoid , perforates, serratus magnus , 
which increase the capacity of the thorax to its utmost limit. 

In Expiration the diameters of the chest are all diminished, viz.: 

1. The vertical , by the ascent of the diaphragm. 

2. The antero-posterior , by a depression of the ribs and sternum. 

In ordinary tranquil expiration the diameters of the thorax are dimin¬ 
ished by the recoil of the elastic tissue of the lungs and the ribs; but in 
forcible expiration the muscles which depress the ribs and sternum, and 
thus further diminish the diameter of the chest, are the internal intercostals, 
the infracostals, and the triangularis sterni. 

In the extraordinary efforts of expiration certain auxiliary muscles are 
brought into play, viz.: the abdominal and sacro-lumbalis muscles, which 
diminish the capacity of the thorax to its utmost limjt. 

Expiration is aided by the recoil of the elastic tissue of the lungs and ribs 
and the pressure of the air. 


RESPIRATION. 


63 


Movements of the Glottis. At each inspiration the rima-glottidis is 
dilated by a separation of the vocal cords, produced by the contraction of 
the crico-arytenoid muscles, so as to freely admit the passage of air into the 
lungs: in expiration they fall passively together, but do not interfere with 
the exit of air from the chest. 

Nervous Mechanism of Respiration. The movements of Respira¬ 
tory muscles, though capable of being modified to a certain extent by 
efforts of the will, are of an automatic character, and called forth by 
nervous impulses emanating from the medulla oblongata. The Respiratory 
centre, the so-called vital point, generates the nerve impulses, which, travel¬ 
ing outward through the phrenic and intercostal nerves, excite contractions 
of the diaphragm and intercostal muscles respectively. This centre is for 
the most part automatic in its action, though it is capable of being modified 
by impulses reflected to it through various sensory nerves. 

This centre may be stimulated — 

1. Directly , by the condition of the blood. An increase of carbonic acid 
or a diminution of oxygen in the blood causes an acceleration of the respi¬ 
ratory movements; the reverse of these conditions causes a diminution of 
the respiratory movements. 

2. Indirectly , by reflex action. The medulla may be excited to action 
through the pneumogastric nerve, by the presence of carbonic acid in the 
lungs irritating its terminal filaments; through the fifth nerve, by irritation 
of the terminal branches; and through the nerves of general sensibility. In 
either case this centre reflects motor impulses to the respiratory muscles 
through the phrenic, intercostals , inferior laryngeal and other nerves. 

Types of Respiration. The abdominal type is most marked in young 
children, irrespective of sex; the respiratory movements being effected by 
the diaphragm and abdominal muscles. 

In the stiperior costal type , exhibited by the adult female, the respiratory 
movements are more marked in the upper part of the chest, from the 1st to 
the 7th ribs, permitting the uterus to ascend in the abdomen during preg¬ 
nancy without interfering with respiration. 

In the inferior costal type , manifested by the male, the movements are 
largely produced by the muscles of the lower portion of the chest, from the 
7th rib downward, assisted by the diaphragm. 

The respiratory movements vary according to age, sleep and exercise, 
being most frequent in early life, but averaging 20 per minute in adult life. 
They are diminished by sleep and increased by exercise. There are about 
four pulsations of the heart to each respiratory act. 


64 


HUMAN PHYSIOLOGY. 


During inspiration two sounds are produced; the one, heard in the 
thorax, in the trachea and larger bronchial tubes, is tubular in character; 
the other, heard in the substance of the lungs, is vesicular in character. 

AMOUNT OF AIR EXCHANGED IN RESPIRATION, AND CAPACITY 

OF LUNGS. 

The Tidal or breathing volume of air, that which passes in and out of the 
lungs at each inspiration and expiration, is estimated at from 20 to 30 cubic 
inches. 

The Complemental air is that amount which can be taken into the lungs 
by a forced inspiration, in addition to the ordinary tidal volume, and 
amounts to about no cubic inches. 

The Reserve air is that which usually remains in the chest after the ordi¬ 
nary efforts of expiration, but which can be expelled by forcible expiration. 
The volume of reserve air is about 100 cubic inches. 

The Residual air is that portion which remains in the chest and cannot 
be expelled after the most forcible expiratory efforts, and which amounts, 
according to Dr. Hutchinson, to about 100 cubic inches. 

The Vital Capacity of the chest indicates the amount of air that can 
be forcibly expelled from the lungs after the deepest possible inspiration, 
and is an index of an individual’s power of breathing in disease and pro¬ 
longed severe exercise. The combined amounts of the tidal, the comple* 
mental and reserve air, 230 cubic inches, represents the vital capacity of an 
individual 5 feet 7 inches in height. The vital capacity varies chiefly with 
stature. It is increased 8 cubic inches for every inch in height above this 
standard, and diminishes 8 cubic inches for each inch below it. 

The Tidal Volume of air is carried only into the trachea and larger 
bronchial tubes by the inspiratory movements. It reaches the deeper 
portions of the lungs in obedience to the law of diffusion of gases, which is 
inversely proportionate to the square root of their densities. 

The ciliary action of the columnar cells lining the bronchial tubes also 
assists in the interchange of air and carbonic acid. 

The entire volume of air passing in and out of the thorax in 24 hours is 
subject to great variation, but can be readily estimated from the tidal 
volume and the number of respirations per minute. Assuming that an 
individual takes into the chest 20 cubic inches at each inspiration, and 
breathes 18 times per minute, in 24 hours there would pass in and out of 
the lungs 518,400 cubic inches, or 300 cubic feet. 

Chemistry of Respiration. As the inspired air undergoes a change 


RESPIRATION. 


65 


in composition during its stay in the lungs which renders it unfit for further 
respiration, it becomes requisite, for the correct understanding of respiration, 
to ascertain the composition of both inspired and expired air. 

Composition of Air. Chemical analysis has shown that every ioo 
vols. of air contains 20.81 vols. of oxygen, and 70.19 vols. of nitrogen, and 
0.03 vol. of carbonic acid. Aqueous vapor is also present, though the 
quantity is variable. The higher the temperature the greater the amount. 

The changes in the air effected by respiration are— 

Loss of oxygen, to the extent of 5 cubic inches per ioo of air, or 1 in 20. 

Gain of carbonic acid, to the extent of 4.66 cubic inches per ioo of 
air or .93 inch in 20. 

Increase of water vapor and organic matter. 

Elevation of temperature. 

Increase and at times decrease of nitrogen. 

Gain of ammonia. 

The total quantity of oxygen withdrawn from the air and consumed by 
the body in 24 hours amounts to 15 cubic feet, and can be readily esti¬ 
mated from the amount consumed at each respiration. Assuming that one 
inch of oxygen remains in the lungs at each respiration, in one hour there 
are consumed 1080 inches, and in 24 hours, 25,920 cubic inches or 15 cubic 
feet, weighing 18 oz. To obtain this quantity, 300 cubic feet of air are 
necessary. 

The quantity of oxygen consumed daily is subject to considerable varia¬ 
tion. It is increased by exercise, digestion and lowered temperature, and 
decreased by the opposite conditions. 

The quantity of carbonic acid exhaled in 24 hours varies greatly. It 
can be estimated in the same way. Assuming that an individual exhales 
•93 + cubic inch at each respiration, in one hour there are eliminated 1008 
cubic inches, and in 24 hours, 24.192 cubic inches or 14 cubic feet, contain¬ 
ing 7 ozs. of pure carbon. 

The exhalation of carbonic acid is increased by muscular exercise; 
nitrogenous food; tea, coffee and rice; age, and by muscular development; 
decreased by a lowering of temperature; repose; gin and brandy, and a 
dry condition of the air. 

As there is always more oxygen consumed than carbonic acid exhaled, 
and as oxygen unites with carbon to form an equal volume of carbonic acid, 
it is evident that a certain quantity of oxygen disappears within the body. 
In all probability it unites with the sulphur hydrogen of the food to form 
water. 


66 


HUMAN PHYSIOLOGY. 


The amount of watery vapor which passes out of the body with the 
expired air amounts to from one to two pounds. 

The organic matter , though slight in amount, gives the odor to the breath. 
In a room with defective ventilation, the organic matter accumulates and 
gives rise to headache, nausea, drowsiness, etc. Long continued breathing 
of such air produces general ill health. It is not so much the presence of 
C 0 2 in increased amount, as the presence of organic matter which neces¬ 
sitates thorough ventilation. 

Condition of the Gases in the Blood. 

Oxygen is absorbed from the lungs into the arterial blood by the coloring 
matter, hcemoglobin , with which it exists in a state of loose combination, 
and is disengaged during the process of nutrition. 

Carbonic acid , arising in the tissues, is absorbed into the blood, in conse¬ 
quence of its alkalinity, where it exists in a state of simple solution and 
also in a state of feeble combination with the carbonates, soda and potassa, 
forming the bicarbonates. 

Nitrogen is simply held in solution in the plasma. 

Exchange of Gases in the Air Cells. From the difference in tension 
of the oxygen in the air cells (27.44 mm. of Hg), and of the oxygen in the 
venous blood (22 mm. Hg), and of the difference of the carbonic acid tension 
in the venous blood (41 mm. Hg), and in the air cells (27 mm. Hg), it might 
be concluded that the passage of the gases might be due solely to pressure. 
The absorption of oxygen, however, does not follow absolutely the law of 
pressures; that chemical processes are involved is shown by the union of 
oxygen with the haemoglobin of the blood corpuscles. The exhalation of 
CO 2 is also partly a chemical process, as it has been shown that the quan¬ 
tity excreted is greatly increased when oxygen is simultaneously absorbed. 
Oxygen not only favors the exhalation of loosely combined C 0 2 ,but favors 
the expulsion of that which can only be excreted by the addition of acids 
to the blood. 

Changes in the Blood during Respiration. 

As the blood passes through the lungs it is changed in color , from the 
dark purple hue of venous blood to the bright red scarlet of arterial 
blood. 

The heterogeneous composition of venous blood is exchanged for the 
uniform composition of the arterial. 

It gains oxygen and loses carbonic acid. 

Its coagulability is increased. Temperature is diminished. 

Asphyxia. If the supply of oxygen to the lungs be diminished and 


ANIMAL HEAT. 


67 


the carbonic acid retained in the blood, the normal respiratory movements 
cease, the condition of asphyxia ensues, which soon terminates in death. 

The phenomena of asphyxia are, violent spasmodic action of the respi¬ 
ratory muscles, attended by convulsions of the muscles of the extremities, 
engorgement of the venous system, lividity of the skin, abolition of sensi¬ 
bility and reflex action, and death. 

The cause of death is a paralysis of the heart, from over distention by 
blood. The passage of the blood through the capillaries is prevented by 
contraction of the smaller arteries, from irritation of the vasomotor centre. 
The heart is enfeebled by a want of oxygen and inhibited in its action by 
the inhibitory centres. 


ANIMAL HEAT. 

The Functional Activity of all the organs and tissues of the body is 
attended by the evolution of heat, which is independent, for the most part, 
of external conditions. Heat is a necessary condition for the due perform¬ 
ance of all vital actions; though the body constantly loses heat by radia¬ 
tion and evaporation , it possesses the capability of renewing it and main¬ 
taining it at a fixed standard. The nortnal temperature of the body in the 
adult, as shown by means of* a delicate thermometer placed in the axilla, 
ranges from 97.25 0 Fahr. to 99.5 0 Fahr., though the mean normal tem¬ 
perature is estimated by Wunderlich at 98.6° Fahr. 

The temperature varies in different portions of the body, according to 
the degree in which oxidation takes place; being the highest in the muscles 
during exercise, in the brain, blood, liver, etc. 

The conditions which produce variations in the normal temperature 
of the body are: age, period of the day, exercise, food and drink, climate, 
season and disease. 

Age. At birth the temperature of the infant is about 1° F. above that of 
the adult, but in a few hours falls to 95.5° F., to be followed in the course 
of 24 hours by a rise to the normal or a degree beyond. During childhood 
the temperature approaches that of the adult; in aged persons the tempera¬ 
ture remains about the same, though they are not as capable of resisting 
the depressing effects of external cold as adults. A diurnal variation of 
the temperature occurs from 1.8° F. to 3.6° F. (Jurgensen); the maximum 
occurring. late in the afternoon, from 4 to 9 P. M., the minimum , early in 
the morning, from I to 7 A. M. 

Exercise. The temperature is raised from i° to 2° F. during active 


68 


HUMAN PHYSIOLOGY. 


contractions of the muscular masses, and is probably due to the increased 
activity of chemical changes; a rise beyond this point being prevented by 
its diffusion to the surface, consequent on a more rapid circulation, radia¬ 
tion, more rapid breathing, etc. 

Food and drink. The ingestion of a hearty meal increases the tempera¬ 
ture but slightly; an absence of food, as in starvation, produces a marked 
decrease. Alcoholic drinks, in large amounts, in persons unaccustomed 
to their use, cause a depression of the temperature, amounting from 1° to 
2° F. Tea causes a slight elevation. 

External temperature. Long continued exposure to cold, especially if 
the body is at rest, diminishes the temperature from i° to 2° F., while 
exposure to a great heat slightly increases it. 

Disease frequently causes a marked variation in the normal temperature 
of the body, rising as high as 107° F. in typhoid fever, and 105° F. in 
pneumonia; in cholera it falls as low as 8o° F. Death usually occurs 
when the heat remains high and persistent, from 106° to no° F.; the 
increase of heat in disease is due to excessive production rather than to 
diminished elimination. 

The source of heat is to be sought for in the chemical decompositions 
and hydrations taking place during the general process of nutrition, and the 
combustion of the carbonaceous compounds by the oxygen of the inspired 
air; the amount of its production is in proportion to the activity of the 
internal changes. 

Every contraction of a muscle, every act of secretion, each exhibition 
of nerve force, is accompanied by a change in the chemical composition of 
the tissues and an evolution of heat. The reduction of the disintegrated 
tissues to their simplest form by oxidation; the combination of the oxygen 
of the inspired air with the carbon and hydrogen of the blood and tissues, 
results in the formation of carbonic acid and water and the generation of a 
large amount of heat. 

Certain elements of the food, particularly the non-nitrogenized substances, 
undergo oxidation without taking part in the formation of the tissues, being 
transformed into carbonic acid and water, and thus increase the sum of 
heat in the body. 

Heat-producing Tissues. All the tissues of the body add to the 
general amount of heat, according to the degree of their activity. But 
special structures on account of their mass and the large amount of blood 
they receive, are particularly to be regarded as heat producers ; e. g. :— 

1. During mental activity the brain receives nearly one-fifth of the 


SECRETION. 


69 


entire volume of blood, and the venous blood returning from it is charged 
with waste matters, and its temperature is increased. 

2. The muscular tissue , on account of the many chemical changes occur¬ 
ring during active contractions, must be regarded as the chief heat- 
producing tissue. 

3. The secreting glands , during their functional activity, add largely to 
the amount of heat. 

The entire quantity of heat generated within the body has been demon¬ 
strated experimentally to be about 2300 calories, a calorie or heat unit 
being that amount of heat required to raise the temperature of one kilo, of 
water (2.2 lbs.) one degree Centigrade. This quantity of heat if not utilized 
and retained within the body would elevate its temperature in 24 hours 
about 6o° F. That this volume of heat depends very largely upon the 
oxidation of the food stuffs can be shown experimentally. 

The normal temperature of the body is maintained by a constant expen¬ 
diture of the heat in several directions:— 

1. In warming the food, drink and air that are consumed in 24 hours. 
For*this purpose about 157 heat units are required. 

2. In evaporating water from the skin and lungs; 619 heat units being 
utilized for this purpose. 

3. In radiation and conduction. By these processes the body loses at 
least 50 per cent, of its heat, or 1156 heat units. 

4. In the production of work; the work of the circulatory, respiratory, 
muscular, and nervous apparatus being performed by the transformation of 
369 heat units into units of work. 

The nervous system influences the production of heat in a part, by 
increasing the amount of blood going through it by its action upon the 
vasomotor nerves. Whether there exists a special heat centre has not 
been satisfactorily determined, though this is probable. 


SECRETION. 

The Process of Secretion consists in the separation of materials from 
the blood which are either to be again utilized to fulfill some special pur¬ 
pose in the economy, or are to be removed from the body as excrementi- 
tious matter; in the former case they constitute the secretions , in the latter, 
the excretions. 

The materials which enter into the composition of the secretions are 
derived from the nutritive principles of the blood, and require special 


70 


HUMAN PHYSIOLOGY. 


organs, e. g., gastric glands, mammary glands, etc., for their proper 
elaboration. 

The materials which compose the excretions preexist in the blood, and 
are the results of the activities of the nutritive process; if retained within 
the body they exert a deleterious influence upon the composition of the 
blood. 

Destruction of a secreting gland abolishes the secretion peculiar to it, 
and it cannot be formed by any other gland; but among the excreting 
organs there exists a complementary relation, so that if the function of one 
organ be interfered with, another performs it to a certain extent. 


CLASSIFICATION OF THE SECRETIONS. 

PERMANENT FLUIDS. 

Serous fluids. Vitreous humor of the eye. 

Synovial fluid. Fluid of the labyrinth of the internal 

Aqueous humor of the eye. ear. 

Cerebro-spinal fluid. 


TRANSITORY FLUIDS. 


Mucus. 

Sebaceous matter. 

Cerumen (external meatus). 
Meibomian fluid. 

Milk and colostrum. 

Tears. 

Saliva. 


Gastric juice. 

Pancreatic juice. 

Secretion from Brunner’s glands. 
Secretion from Leiberkiihn’s glands. 
Secretions from follicles of the large 
intestine. 

Bile (also .an excretion). 


EXCRETIONS. 

Perspiration and the secretion of Urine. 

the axillary glands. Bile (also a secretion). 


FLUIDS CONTAINING FORMED ANATOMICAL ELEMENTS. 
Seminal fluid, containing spermatozoids. Fluid of the Graafian follicles. 


The essential apparatus for secretion is a delicate, homogeneous, 
structureless membrane , on one side of which, in close contact, is a capil¬ 
lary plexus of blood vessels , and on the other side a layer of cells whose 
physiological function varies in different situations. 

Secreting organs may be divided into membranes and glands . 

Serous membranes usually exist as closed sacs, the inner surface of which 
is covered by pale, nucleated epithelium, containing a small amount of 
secretion. 


SECRETIONS. 71 

The serous membranes are the pleura,peritoneum,pericardium, synovial 
sacs, etc. 

The serous fluids are of a pale amber color, somewhat viscid, alkaline, 
coagutable by heat, and resemble the serum of the blood; their amount 
is but small; the pleural varies from 4 to 7 drachms; the peritoneal from 
I to 4 ounces ; the pericardial from 1 to 3 drachms. 

The synovial fluid is colorless, alkaline, and extremely viscid, from the 
presence of synovine. 

The function of serous fluids is to moisten the opposing surfaces, so as to 
prevent friction during the play of the viscera. 

The mucous membranes are soft and velvety in character, and line the 
cavities and passages leading to the exterior of the body, e.g., the gastro¬ 
intestinal, pulmonary and genito-urinary. They consist of a primary 
basement membrane covered with epithelial cells, which in some situations 
are tessellated, in others, columnar. 

Mucus is a pale, semi-transparent, alkaline fluid, containing epithelial 
cells and leucocytes. It is composed, chemically, of water, an albuminous 
principle, mucosine, and mineral salts; the principal varieties are nasal, 
bronchial, vaginal and urinary. 

Secreting Glands are formed of the same elements as the secreting 
membranes; but instead of presenting flat surfaces, are involuted, forming 
tubules, which may be simple follicles, e.g., mucous, uterine or intestinal; 
or compound follicles, e.g., gastric glands, mammary glands; or racemose 
glands, e.g., salivary glands and pancreas. They are composed of a base¬ 
ment membrane, enveloped by a plexus of blood vessels, and are lined by 
epithelial and true secreting cells, which in different glands possess the 
capability of elaborating elements characteristic of their secretions. 

In the production of the secretions two essentially different processes 
are concerned:— 

1. Chemical. The formation and elaboration of the characteristic organic 
ingredients of the secreted fluids, e.g., pepsin, pancreatin, takes place 
during the intervals of glandular activity, as a part of the general function 
of nutrition. They are formed by the cells lining the glands, and can often 
be seen in their interior with the aid of the microscope, e.g., bile in the 
liver cells, fat in the cells of the mammary gland. 

2. Physical. Consisting of a transudation of water and mineral salts 
from the blood into the interior of the gland. 

During the intervals of glandular activity, only that amount of blood 
passes through the gland sufficient for proper nutrition; when the gland 


72 


HUMAN PHYSIOLOGY. 


begins to secrete, under tbe influence of an appropriate stimulus, the blood 
vessels dilate and the quantity of blood becomes greatly increased beyond 
that flowing through the gland during its repose. 

Under these conditions a transudation of water and salts takes place, 
washing out the characteristic ingredients, which are discharged by the 
gland ducts. The discharge of the secretions is intermittent; they are 
retained in the glands until they receive the appropriate stimulus, when 
they pass into the larger ducts by the vis-a-tergo, and are then discharged 
by the contraction .of the muscular walls of the ducts. 

The activity of glandular secretion is hastened by an increase in the 
blood pressure and retarded by a diminution. 

The nervous centres in the medulla oblongata influence secretion, (i) by 
increasing or diminishing the amount of blood entering a gland ; (2) by 
exerting a direct influence upon the secreting cells themselves, the centres 
being excited by reflex irritation, mental emotion, etc. 


MAMMARY GLANDS. 

The Mammary Glands secrete the milk, and undergo at different 
periods of life remarkable changes in structure. Though rudimentary in 
childhood, they gradually increase in size as the young female approaches 
puberty. 

The gland presents, at its convexity, a small prominence of skin, the 
nipple , surrounded by an areola of a deeper tint. It is covered anteriorly 
by a layer of adipose tissue and posteriorly by a fibrous structure which 
attaches it loosely to the pectoralis muscle. 

During utero-gestation the mammae become large, firm, well-developed 
and lobulated; the areola becomes darker and the veins more prominent. 
In the intervals of lactation the glands gradually sink in size to their 
original condition, undergo involution, and become non-secreting organs. 

Structure of the Mammae. The mamma is a conglomerate gland, 
consisting of a number of lobes, from 15 to 20 in number, each of which 
is subdivided into lobules made up of gland vesicles or acini. The ducts 
which convey the secretion to the exterior, the lactiferous ducts , open by 
15 to 20 orifices upon the surface of the nipple, at tbe base of which they 
are dilated to form little reservoirs in which the milk collects during the 
periods of active secretion. 

The walls of the lacteal duct consist of white, fibrous tissue, and non- 
striated muscular fibres, lined by short columnar cells, which disappear 
during active lactation. The ducts measure about the ^ of an inch in 


MILK. 


73 


diameter; as they pass into the substance of the gland, each duct divides 
into a number of branches, which are distributed to distinct lobules and 
terminate in the acini. 

An acinus is made up of a number of vesicles composed of a homoge¬ 
neous membrane, lined by pavement epithelium. The gland vesicles are 
held together by white, fibrous tissue, which unites the lobules into lobes. 


MILK. 

Milk has a pale blue color, is almost inodorous, of a sweetish taste, an 
alkaline reaction, and a specific gravity varying from 1.025 to 1-046. 
Examined microscopically it is seen to contain an immense number of 
globules, measuring the of an inch in diameter, suspended in a clear 

fluid; these are the milk globules , formed of a small mass of oily matter 
covered by a layer of albumin. 

The quantity of milk secreted by the human female in 24 hours, during 
the period of lactation, is about two to three pints ; the quantity removed by 
the infant from a full breast at one time being about two ounces. 

COMPOSITION OF MILK. 


Water,.890.00 

Proteids, including casein and serum albumin, . . . 35-00 

Fatty matter (butter),. 25.00 

Sugar (lactose) with extractives,. 48.00 

Salts,. 2.00 


1000.00 

Casein is the nutritive principle of milk, and constitutes its most important 
ingredient. It is held in solution by an alkali, but upon the addition of an 
acid it undergoes coagulation, passing into a semi-solid form. The presence 
oflactic acid, resulting from a transformation of milk sugar, causes spon¬ 
taneous coagulation to take place. 

The Fatty matter is more or less solid at ordinary temperature, and con¬ 
sists of margarine and oleine; when subjected to the churning process the 
globules run together and form a coherent mass, the butter. 

When milk is allowed to stand for a varying length of time, the fat 
globules rise to the surface, forming a layer more or less thick, the cream. 

Milk sugar or lactose is an important ingredient in the food of the young 
child; it is readily transformed into lactic acid in the presence of nitrogen- 
ized ferments. 

F 







74 


HUMAN PHYSIOLOGY. 


Influences modifying the secretion. During lactation there is a 
demand for an increased amount of fluid, and if not supplied, the amount 
of milk secreted is diminished. Good food in sufficient quantity is neces¬ 
sary for the proper elaboration of milk, though no particular article influ¬ 
ences its production. 

Mental emotion at times influences the character of the milk, decreasing 
the amount of its different constituents. 

Mechanism of Secretion. The water and salts preexist in the blood 
and pass into the gland vesicles by osmosis. The casein, fatty matter and 
sugar appear only in the mammary gland, but the mechanism of their 
formation is not understood. 

Colostrum is a yellowish, opaque fluid, formed in the mammary glands 
toward the latter period of utero-gestation; it consists of water, albumin, 
fat, sugar and salts, and acts as a laxative to the newly-born infant. 


VASCULAR OR DUCTLESS GLANDS. 

The Vascular Glands are regarded as possessing the power of acting 
upon certain elements of the food and aiding the process of sanguinifica- 
tion; of modifying the composition of the blood as it flows through then- 
substance, by some act of secretion. 

The vascular glands are the spleen , supra-renal capsules , thyroid and 
thymus glands. 

The Spleen is about 5 inches in length, 6 ounces in weight, of a dark 
bluish color, and situated in the left hypochondriac region. It is covered 
externally by a reflection of the peritoneum, beneath which is the proper 
fibrous coat, composed of areolar and elastic tissue and non-striated muscu¬ 
lar fibres. From the inner surface of the fibrous envelope processes or tra¬ 
beculae are given off, which penetrate the substance of the gland, forming a 
network, in the meshes of which is contained the spleen pulp. The splenic 
artery divides into a number of branches, some of which, when they become 
very minute, pass directly into veins, while others terminate in true capillaries. 

As the capillary vessels ramify through the substance of the gland, their 
walls frequently disappear and the blood passes from the arteries into the 
veins through lacunce (Gray). 

The splenic or Malpighian corpuscles are small bodies, spherical or 
ovoid in shape, the fa of an inch in diameter, situated upon the sheaths of 
the small arteries. They consist of a delicate membrane, containing a 


VASCULAR OR DUCTLESS GLANDS. 


75 


semi-fluid substance composed of numerous small cells resembling lymph 
corpuscles. The spleen pulp is a dark red, semi-fluid substance, of a soft 
consistence, contained in the meshes of the trabeculae. In it are found 
numerous corpuscles, like those observed in the Malpighian bodies, blood 
corpuscles in a natural and altered condition, nuclei and pigment granules. 

Function of the Spleen, Probably influences the preparation of the 
albuminous food for nutrition; during digestion the spleen becomes larger, 
its contents are increased in amount, and after digestion it gradually dimin¬ 
ishes in size, returning to the normal condition. 

The red corpuscles are here disintegrated, after having fulfilled their 
function in the blood; the splenic venous blood containing relatively a 
small quantity. 

The white corpuscles appear to be increased in number, the blood of the 
splenic vein containing an unusually large proportion. 

The spleen serves also as a reservoir for blood when the portal circula¬ 
tion becomes obstructed. 

The nervous system controls the enlargement of the spleen; division of 
the nerve produces dilatation of the vessels, stimulation contracts them. 

The Supra-renal Capsules are triangular, flattened bodies, situated 
above the kidney. They are invested by a fibrous capsule sending in 
trabeculae, forming the framework. The glandular tissue is composed of 
two portions, a cortical and medullary. The cortical being made up of 
small cylinders lined by cells and containing an opaque mass, nuclei and 
granular matter. The medullary consists of a fibrous network containing 
in the alveoli nucleated protoplasm. 

The Thyroid gland consists of a fibrous stroma, containing ovoid 
closed sacs, measuring on the average -fa of an inch, formed of a delicate 
membrane lined by cells; the contents of the sacs consist of yellowish 
albuminous fluid. 

The Thymus gland is most developed in early life and almost disap¬ 
pears in the adult. It is divided by processes of fibrous tissue into lobules, 
and these again into follicles which contain lymphoid corpuscles. 

The functions of the vascular organs appear to be the more complete 
elaboration of the blood necessary for proper nutrition; they are most highly 
developed during infancy and embryonic life, when growth and develop¬ 
ment are most active. 


76 


HUMAN PHYSIOLOGY. 


EXCRETION. 

The Principal Excrementitious Fluids discharged from the body 
are the urine, perspiration and bile; they hold in solution principles of 
waste which are generated during the activity of the nutritive process, and 
are the ultimate forms to which the organic constituents are reduced in the 
body. They also contain inorganic salts. 

The Urinary Apparatus consists of the kidneys, ureters and bladder. 


KIDNEYS. 

The Kidneys are the organs for the secretion of urine; they resemble 
a bean in shape, are from four to five inches in length, two in breadth, and 
weigh from four to six ounces. 

They are situated in the lumbar region, one on each side of the vertebral 
column, behind the peritoneum, and extend from the nth rib to the crest 
of the ilium; the anterior surface is convex, the posterior surface concave, 
the latter presenting a deep notch, the hilus. 

The kidney is surrounded by a thin, smooth membrane composed of 
white fibrous and yellow elastic tissue; though it is attached to the surface 
of the kidney by minute processes of connective tissue it can be readily torn 
away. The substance of the kidney is dense but friable. 

Upon making a longitudinal section of the kidney it will be observed 
that the hilus extends into the interior of the organ and expands to form 
a cavity known as the sinus. This cavity is occupied by the upper 
dilated portion of the ureter, the interior of which forms the pelvis. 

. The ureter subdivides into several portions, which ultimately give origin 
to a number of smaller tubes termed calyces , which receive the apices of 
the pyramids. 

The Parenchyma of the Kidney consists of two portions, viz :— 

1. An internal or medullary portion , consisting of a series of pyramids 
or cones, some twelve or fifteen in number. They present a distinctly stri¬ 
ated appearance, a condition due to the straight direction of the tubules and 
blood vessels. 

2. An external or cortical portion , consisting of a delicate matrix con¬ 
taining an immense number of tubules having a markedly convoluted 
appearance. Throughout its structure are found numerous small ovoid 
bodies termed Malpighian corpuscles. 


KIDNEYS. 


77 



The Uriniferous Tubules. The kidney is a compound tubular gland 
composed of microscopic tubules, whose function it is to secrete from the 

Fig. 9 . 


LONGITUDINAL SECTION THROUGH THE KIDNEY, THE PELVIS OF THE KIDNEY, AND A 

NUMBER OF RENAL CALYCES. 

A, branch of the renal artery; U, ureter; C, renal calyx; 1, cortex; 1', medullary 
rays; 1", labyrinth, or cortex proper ; 2, medulla ; 2', papillary portion of medulla, 
or medulla proper; 2", border layer of the medulla; 3, 3, transverse section through 
the axes of the tubules of the border layer; 4, fat of the renal sinus; 5, 5, arterial 
branches; *, transversely coursing medulla rays.— Tyson, after Henle. 


blood those waste products which collectively constitute the urine. If the 
apex of each pyramid be examined with a lens, it will present a number 









78 


HUMAN PHYSIOLOGY. 


of small' orifices which are the beginnings of the uriniferous tubules. 
From this point the tubules pass outward in a straight but somewhat 
diverging manner toward the cortex, giving off at 
acute angles a number of branches (Fig. io). From 
the apex to the base of the pyramids they are 
known as the tubules of Bellini. In the cortical 
portion of the kidney each tubule becomes en¬ 
larged and twisted, and after pursuing an extremely 
convoluted course, turns backward into the medul¬ 
lary portion for some distance, forming the descend¬ 
ing limb of Henle’s loop; it then turns upon itself, 
forming the ascending limb of the loop, reenters 
the cortex, again expands, and finally terminates in 
a spherical enlargement known as Muller’s or Bow¬ 
man's capsule. Within this capsule is contained a 
small tuft of blood vessels constituting the glomerulus 
or Malpighian corpuscle. 

Structure of the Tubules. Each tubule consists 

of a basement membrane lined by epithelial cells 

throughout its entire exetnt. The tubule and its 

contained epithelium vary in shape and size in different 

parts of its course. The termination of the convoluted 

. tube consists of a little sac or capsule, which is ovoidal 
Diagrammatic exposi- A 

tion of the method in shape and measures about of an inch in size. 

rous h tub^unite^to This capsule is lined by a layer of flattened epithelial 

form primitive cones. ce lls w hich is also reflected over the surface of the 
— Tyson , after Lud¬ 
wig. glomerulus. During the periods of secretory activity, 

the blood vessels of the glomerulus become filled with 
blood, so that the cavity of the sac is almost obliterated; after secretory 
activity the blood vessels contract and the sac cavity becomes enlarged. 
In that portion of the tubule lying between the capsule and Henle’s loop 
the epithelial cells are cuboidal in shape; in Henle’s loop they are flattened, 
while in the remainder of the tubule they are cuboidal and columnar. 

Blood vessels of the Kidney. The renal artery is of large size and 
enters the organ at the hilum; it divides into several large branches, which 
penetrate the substance of the kidney, between the pyramids, at the base 
of which they form an anastomosing plexus, which completely surrounds 
them. From this plexus vessels follow the straight tubes toward the apex, 
while others, entering the cortical portion, divide into small twigs which 


















KIDNEYS. 


79 


enter the Malpighian body and form a mass of convoluted vessels, the 
glomerulus. After circulating through the Malpighian tuft, the blood is 
gathered together by two or three small veins, which again subdivide and 
form a fine capillary plexus, which envelops the convoluted tubules; from 
this plexus the veins converge to form the emulgent vein, which empties 
into the vena cava. 

The nerves of the kidney follow the course of the blood vessels and 
are derived from the renal plexus. 

The Ureter is a membranous tube, situated behind the peritoneum, 
about the diameter of a goose quill, 18 inches in length, and extends from 
the pelvis of the kidney to the base of the bladder, which it perforates in 
an oblique direction. It is composed of 3 coats, fibrous, muscular and 
mucous. 

The Bladder is a reservoir for the temporary reception of the urine 
prior to its expulsion from the body; when fully distended it is ovoid in 
shape, and holds about one pint. It is composed of four coats, serous , 
muscular , the fibres of which are arranged longitudinally and circularly, 
areolar and mucous. The orifice of the bladder is controlled by the 
sphincter vesicce , a muscular band about half an inch in width. 

As soon as the urine is formed it passes through the tubuli uriniferi 
into the pelvis, and from thence through the ureters into the bladder, which 
it enters at an irregular rate. Shortly after a meal, after the ingestion of 
large quantities of fluid, and after exercise, the urine flows into the blad¬ 
der quite rapidly, while it is reduced to a few drops during the intervals of 
digestion. It is prevented from regurgitating into the ureters on account of 
the oblique direction they take between the mucous and muscular coats. 

Nervous Mechanism of Urination. When the urine has passed into 
the bladder, it is there retained by the sphincter vesicse muscle, kept in a 
state of tonic contraction by the action of a nerve centre in the lumbar 
region of the spinal cord. This centre can be inhibited and the sphincter 
relaxed, either reflexly , by impressions coming through sensory nerves from 
the mucous membrane of the bladder, or directly , by a voluntary impulse 
descending the spinal cord. When the desire to urinate is experienced, 
impressions made upon the vesical sensory nerves are carried to the centres 
governing the sphincter and detrusor urince muscles and to the brain. If 
now the act of urination is to take place, a voluntary impulse, originating 
in the brain, passes down the spinal cord and still further inhibits the 
sphincter vesicse centre, with the effect of relaxing the muscle, and of 
stimulating the centre governing the detrusor muscle, with the effect of con- 


80 


HUMAN PHYSIOLOGY. 


tracting the muscle and expelling the urine. If the act is to be sup¬ 
pressed, voluntary impulses inhibit the detrusor centre and possibly stimu¬ 
late the sphincter centre. 

The genito-spinal centre controlling these movements is situated in that 
portion of the spinal cord corresponding to the origin of the 3d, 4th and 
5th sacral nerves. 


URINE. 


Normal Urine is of a pale yellow or amber color, perfectly transparent, 
with an aromatic odor, an acid reaction, a specific gravity of 1.020, and a 
temperature when first discharged of ioo° Fahr. 

The color varies considerably in health, from a pale yellow to a brown 
hue, due to the presence of the coloring matter, urobilin or urochroine. 

The transparency is diminished by the presence of mucus, the calcium 
and magnesium phosphates and the mixed urates. 

The reaction of the urine is acid, owing to the presence of acid phos¬ 
phate of sodium. The degree of acidity, however, varies at different 
periods of the day. Urine passed in the morning is strongly acid, while 
that passed during and after digestion, especially if the food is largely vege¬ 
table in character, is either neutral or alkaline. 

The specific gravity varies from 1.015 to 1.025. 

The quantity of urine excreted in 24 hours is between 40 and 50 fluid 
ounces, but ranges above and below this standard. 

The odor is characteristic, and caused by the presence of taurylic and phe- 
nylic acids, but is influenced by vegetable foods and other substances elimi¬ 
nated by the kidneys. 


COMPOSITION OF URINE. 

Water,... 

Urea,. 

Other nitrogenized crystalline bodies, uric acid, prin¬ 
cipally in the form of alkaline urates. 

Creatin, creatinin, xanthin, hypoxanthin. 

Hippuric acid, leucin, tyrosin, taurin, cystin, all in 
small amounts, and not constant. 

Mucus and pigment. 

Salts :— 

Inorganic , principally sodium and potassium sul¬ 
phates, phosphates and chlorides, with magnesium 
and calcium phosphates, traces of silicates and 
chlorides. 

Organic ; lactates, hippurates, acetates, formates, 
which appear only occasionally. 

Sugar,. 

Gases (nitrogen and carbonic acid principally). 


967. 

14.230 

10.635 


8.135 


a trace. 


1000.00 








URINE. 


81 


The Average Quantity of the principal constituents excreted in 24 
hours is as follows:— 


Water,.52 fluid oz. 

Urea,. 512.4 grains. 

Uric acid,. 8.5 “ 

Phosphoric acid,. .45.0 “ 

Sulphuric acid,. 31.11“ 

Inorganic salts,...323.25 “ 

Lime and magnesia,. 6.5 “ 


To Determine the amount of solid matters in any given amount of 
urine, multiply the last two figures of the specific gravity by the coefficient 
of Haeser, 2.33; e. g., in 1000 grains of urine having a specific gravity 
1.022, there are contained 22 X 2.33 = 51*26 grains of solid matter. 

Organic Constituents of Urine. Urea is one of the most important 
of the organic constituents of the urine, and is present to the extent of from 
2.5 to 3.2 per cent. Urea is a colorless, neutral substance, crystallizing to 
four-sided prisms terminated by oblique surfaces. When crystallization is 
caused to take place rapidly, the crystals take the form of long, silky 
needles. Urea is soluble in water and alcohol; when subjected to pro¬ 
longed boiling it is decomposed, giving rise to carbonate of ammonia. In 
the alkaline fermentation of urine, urea takes up two molecules of water 
with the production of carbonate of ammonia. 

The average amount of urea excreted daily has been estimated at about 
500 grains. As urea is one of the principal products of the breaking up of 
the albuminous compounds within the body, it is quite evident that the 
quantity produced and eliminated in 24 hours will be increased by any 
increase in the amount of albuminous food consumed, by a rapid destruc¬ 
tion of albuminous tissues, as is witnessed in various pathological states, in¬ 
anition, febrile conditions, fevers, etc. A farinaceous or vegetable diet will 
diminish the urea production nearly one-half. 

Muscular exercise when the nutrition of the body is in a state of equi¬ 
librium does not seem to increase the quantity of urea. 

Seat of Urea Formation. As to the seat of urea formation, little 
is positively known. It is quite certain that it preexists in the blood and is 
merely excreted by the kidneys. It is not produced in muscles, as even 
after prolonged exercise hardly a trace of urea is to be found in them. 
Experimental and pathological facts point to the liver as the probable organ 
engaged in urea formation. Acute yellow atrophy of the liver, suppurative 
diseases of the liver diminish almost entirely the production of urea. 









82 


HUMAN PHYSIOLOGY. 


Uric acid is also a constant ingredient of the urine and is closely allied 
to urea. It is a nitrogenized substance, carrying out of the body a large 
quantity of nitrogen. The amount eliminated daily varies from 5 to io 
grains. Uric acid is a colorless crystal belonging to the rhombic system. 
It is insoluble in water, and if eliminated in excessive amounts it is de¬ 
posited as a “ brick-red ” sediment in the urine. It is doubtful if uric acid 
exists in a free state, being combined for the most part with sodium and 
potassium bases forming urates. It is to be regarded as one of the termi¬ 
nal products of the disassimilation of albuminous compounds, and is prob¬ 
ably produced in the liver. 

Hippuric acid is found very generally in urine, though it is present 
only in small amounts. It is increased by a diet of asparagus, cranberries, 
plums and by the administration of benzoic and cinnamic acids. It is 
probably formed in th*e kidney. 

Kreatinin resembles the kreatin derived from muscles. It is a colorless 
crystal, belonging to the rhombic system. Its origin is unknown, though it 
is largely increased in amount by albuminous food. About 15 grains are 
excreted daily. 

Xanthin, Sarkin, Oxaluric Acid and Allantoin are also constituents 
of urine. They are nitrogenized compounds and are also terminal products 
of albuminous compounds. 

Urobilin, the coloring matter of the urine, is a derivative of the bile pig¬ 
ments. It is particularly abundant in febrile conditions, giving to the urine 
its reddish-yellow color. 

Inorganic Constituents of Urine. Earthy Phosphate. Phos¬ 
phoric acid in combination with magnesium and calcium is excreted daily 
to the extent of from 15 to 30 grains. The phosphates are insoluble in 
water, but are held in solution in the urine by its acid ingredients, alkalinity 
of the urine being attended with a copious precipitation of the phosphates. 
Mental work increases the amount of phosphoric acid excreted, a condition 
caused by increased metabolism of the nervous tissue. 

Sulphuric acid in combination with sodium and potassium constitute the 
sulphates, of which about 30 grains are excreted daily. Sulphuric acid 
results largely from the decomposition of albuminous food and from 
increased destruction of animal tissues. 

The Gases of the urine are carbonic acid and nitrogen. 

Mechanism of Urinary Secretion. As the kidney anatomically pre¬ 
sents an apparatus for filtration (the Malpighian bodies), and an apparatus 


LIVER. 


83 


for secretion (the epithelial cells of the urinary tubules), it might be inferred 
that the elimination of the constituents of the urine is accomplished by the 
twofold process of filtration and secretion; that the water and highly 
diffusible inorganic salts simply pass by diffusion through the walls of the 
blood vessels of the glomerulus into the capsule of Muller, while the urea 
and remaining organic constituents are removed by true secretory action of 
the renal epithelium. Modern experimentation supports this view of renal 
action. 

The secretion of urine is therefore partly physical and partly vital. 

The Filtration of urinary constituents from the glomerulus into Muller’s 
capsule depends largely upon the blood pressure and the rapidity of blood 
flow in the renal artery and glomerulus. Among the influences which 
increase the pressure and velocity, may be mentioned increased frequency 
and force of the heart’s action, contraction of the capillary vessels of the 
body generally, dilatation of the renal artery, increase in the volume of the 
blood. 

The reverse conditions lower the blood pressure and diminish the secre¬ 
tion of urine. 

The elimination of the organic matters by secretory activity of the renal 
epithelium seems to be well established by modern experiments. These 
substances, removed from the blood in the secondary capillary plexus of 
blood vessels, by a true selective action of the epithelium, are dissolved and 
washed toward the pelvis by the liquid coming from the capsules. 

The blood supply to the kidney is regulated by the nervous system. If 
the renal nerves be divided, the renal artery dilates and a copious flow of 
urine takes place. If the peripheral ends of the same nerves be stimulated, 
the artery contracts and the urinary flow ceases. The same is true of the 
splanchnic nerves, through which the vasomotor nerves coming from the 
medulla oblongata and spinal cord pass to the renal plexus. 


LIVER. 

The Liver is a highly vascular, conglomerate gland, appended to the 
alimentary canal. It is the largest gland in the body, weighing about 4^ 
pounds; it is situated in the right hypochondriac region, and retained in 
position by five ligaments, four of which are formed by duplicatures of the 
peritoneal investment. 

The proper coat of the liver is a thin but firm fibrous membrane, closely 
adherent to the surface of the organ, which it penetrates at the transverse 


84 


HUMAN PHYSIOLOGY. 


fissure, and follows the vessels in their ramifications through its substance, 
constituting Glisson's capsule. 

Structure of the Liver. The liver is made up of a large number of 
small bodies, the lobules , rounded or ovoid in shape, measuring the of 
an inch in diameter, separated by a space in which are situated blood 
vessels, nerves, hepatic ducts and lymphatics. 

The lobules are composed of cells, which,- when examined microscopi¬ 
cally, exhibit a rounded or polygonal shape, and measure, on the average, 
the of an inch in diameter; they possess one, and at times two, nuclei; 
they also contain globules of fat, pigment matter, and animal starch. The 
cells constitute the secreting structure of the liver, and are the true hepatic 
cells. 

The Blood vessels which enter the liver are (i) The portal vein , 
made up of the gastric , splenic , superior and inferior mesenteric veins; (2) 
the hepatic artery , a branch of the coeliac axis; both of which are invested 
by a sheath of areolar tissue; the vessels which leave the liver are the 
hepatic veins , originating in its interior, collecting the blood distributed by 
the portal vein and hepatic artery, and conducting it to the ascending vena 
cava. 

Distribution of Vessels. The portal vein and hepatic artery , upon 
entering the liver, penetrate its substance, divide into smaller and smaller . 
branches, occupy the spaces between the lobules, completely surrounding 
and limiting them, and constitute the interlobular vessels. The hepatic 
artery , in its course, gives off branches to the walls of the portal vein and 
Glisson’s capsule, and finally empties into the small branches of the portal 
vein in the interlobular spaces. 

The interlobular vessels form a rich plexus around the lobules, from 
which branches pass to neighboring lobules and enter their substance, 
where they form a very fine network of capillary vessels, ramifying over 
the hepatic cells, in which the various functions of the liver are performed. 
The blood is then collected by small veins, converging toward the centre 
of the lobule, to form the intralobular vein, which runs through its long 
axis and empties into the sub-lobular vein. The hepatic veins are formed 
by the union of the sub-lobular veins, and carry the blood to the ascending 
vena cava; their walls are thin and adherent to the substance of the 
hepatic tissue. 

The Hepatic Ducts or Bile Capillaries originate within the lobules, 
in a very fine plexus lying between the hepatic cells; whether the smallest 
vessels have distinct membranous walls, or whether they originate in the 


LIVER. 


85 


spaces between the cells by open orifices, has not been satisfactorily deter¬ 
mined. 

The Bile Channels empty into the interlobular ducts, which measure 
about of an inch in diameter, and are composed of a thin homogeneous 
membrane lined by flattened epithelial cells. 

As the interlobular bile ducts unite to form larger trunks, they receive 
an external coat of fibrous tissue, which strengthens their walls; they 
finally unite to form one large duct, the hepatic duct , which joins the cystic 
duct; the union of the two forms the ductus communis choledochus , which 
is about three inches in length, the size of a goose quill, and opens into the 
duodenum. 

The Gall Bladder is a pear-shaped sack, about four inches in length, 
situated in a fossa on the under surface of the liver. It is a reservoir for 
the bile, and is capable of' holding about one ounce and a half of fluid. It 
is composed of three coats, (i) serous, a reflection of the peritoneum, (2) 
fibrous and muscular, (3) mucous. 

Functions of the Liver. The liver is a complex organ having a 
variety of relations to the general processes of the body. While its physio¬ 
logical actions are not yet wholly understood, it may be said that it— 

1. Secretes bile. 

2. Forms glycogen. 

3. Assists in the formation of urea and allied products. 

4. Modifies the composition of the blood as it passes through it. 

The Secretion of Bile. The characteristic constituents of the bile do 
not preexist in the blood, but are formed within the interior of the liver 
cells out of materials derived from the venous and arterial blood. The 
hepatic cells absorbing these’materials elaborate them into bile elements, and 
in so doing undergo histological changes similar to those exhibited by other 
secretory glands. The bile once formed, it passes into the mouths of 
the bile capillaries, near the periphery of the lobules. Under the influence 
of the vis-a-tergo of the new formed bile it flows from the smaller into the 
larger bile ducts, and finally empties into the intestine, or is regurgitated 
into the gall bladder, where it is stored up until it is required for the 
digestive process in the small intestine. The study of the secretion of bile 
by means of biliary fistulse reveals the facts that the secretion is continuous 
and not intermittent; that the hepatic cells are constantly pouring bile into 
the ducts which convey it into the gall bladder. As this fluid is required 
only during intestinal digestion, it is only then that the walls of the gall 
bladder contract and discharge it into the intestine. 


86 


HUMAN PHYSIOLOGY. 


The flow of bile from the liver cells into the gall bladder is accomplished 
by the inspiratory movements of the diaphragm, the contraction of the mus¬ 
cular fibres of the biliary ducts, as well as the vis-a-tergo of new formed 
bile. Any obstacle to the outflow of bile into the intestine leads to an accu¬ 
mulation within the bile ducts. The pressure within the ducts increasing 
beyond that of the blood within the capillaries, a re absorption of biliary 
matters by the lymphatics takes place, giving rise to the phenomena of 
jaundice. 

The Bile is both a secretion and an excretion ; it contains new constitu¬ 
ents which are formed only in the substance of the liver, and are destined 
to play an important part ultimately in nutrition ; it contains also waste 
ingredients which are discharged into the intestinal canal and eliminated 
from the body. 

Glycogenic Function. In addition to the preceding function, Ber¬ 
nard, in 1848, demonstrated the fact that the liver, during life, normally 
produces a sugar-forming substance, analogous in its chemical composition 
to starch, which he terms glycogen; also that when the liver is removed 
from the body, and its blood vessels thoroughly washed out, after a few 
hours sugar again makes its appearance, in abundance. 

It can be shown to exist in the blood of the hepatic vein as well as in a 
decoction of the liver substance, by means of either Trommer’s or Fehling’s 
tests, even when the blood of the portal vein does not contain a trace of 
sugar. 

Origin and Destination of Glycogen. Glycogen appears to be 
formed de novo in the liver cells, from materials derived from the food, 
whether the diet be animal or vegetable, though a larger per cent, is 
formed when the animal is fed on starchy and saccharine, than when fed on 
animal food. The glucose , which is one of the products of digestion, is 
absorbed by the blood vessels, and carried directly into the liver; as it does 
not appear in the urine, as it would if injected at once into the general cir¬ 
culation, it is probable that it is detained in the liver, dehydrated and stored 
up as glycogen. The change is shown by the following formula:— 

Glucose. Water. Glycogen. 

C 2 Hi 2 0 6 H 2 0 = C 6 H j 0 O 5 . 

The glycogen thus formed is stored up in the hepatic cells for the future 
requirements of the system. When it is carried from the liver it is again 
transformed into glucose by the agency of a ferment. Glycogen does not 
undergo oxidation in the blood; this takes place in the tissues, particularly 


LIVER. 87 

in the muscles, where it generates heat and contributes to the development 
of muscular force. 

Glycogen, when obtained from the liver, is an amorphous, starch-like 
substance, of a white color, tasteless and colorless, and soluble in water; by 
boiling with dilute acids, or subjected to the action of an animal ferment, 
it is easily converted into glucose. When an excess of sugar is generated 
by the liver, it can be found, not only in the blood of the hepatic vein, 
but also in other portions of the body; under these circumstances it is 
eliminated by the kidneys, appearing in the urine, constituting the condition 
of glycosuria. 

Formation of Urea. The liver is now regarded by many physiologists 
to be the principal organ concerned in urea formation. The liver normally 
contains a certain amount of urea, and if blood be passed through the 
excised liver of an animal which has been in full digestion, a large amount 
of urea is obtained. The clinical evidence proves that in destructive dis¬ 
eases of the liver substance there is at once a falling off in urea elimination. 
Various drugs which increase liver action increase the urea in the urine. 

Elaboration of Blood. Besides the capability of secreting bile, the 
liver possesses the property of so acting upon and modifying the chemical 
composition of the products of digestion, as they traverse its substance, 
that they readily assimilate with the blood, and are transformed into mate¬ 
rials capable of being converted into the elements of the blood and solid 
tissues. 

The albuminose particularly requires the modifying influence of the 
liver; for if it be removed from the portal vein and introduced into the 
jugular vein, it is at once removed from the blood by the action of the 
kidneys. 

The blood of the hepatic vein differs from the blood of the portal vein, 
in being richer in blood corpuscles, both red and white; its plasma is more 
dense, containing a less percentage of water and a greater amount of solid 
constituents, but no fibrin; its serum contains less albumin, fats and salts, 
but its sugar is increased. 

Influence of the Nervous System. The nervous system directly 
controls the functional activity of the liver, and more especially its glyco¬ 
genic function. It was discovered by Bernard that puncture of the medulla 
oblongata is followed by such an enormous production of sugar that it is at 
once excreted by the kidneys, giving rise to diabetic or saccharine urine. 
This part of the medulla is, however, the vasomotor centre for the blood 
vessels of tfte liver. Destruction of this centre, or injury to the vasomotor 


88 


HUMAN PHYSIOLOGY. 


nerves emanating from it in any part of their course, is followed at once by 
dilatation of the hepatic blood vessels, slowing of the blood current, a pro¬ 
found disturbance of the normal relation existing between the blood and 
liver cells, and a production of sugar. Many of the hepatic vasomotor 
nerves may be traced down the cord as far as the lumbar region, while 
others leave the cord high up in the neck and enter the cervical ganglia of 
the sympathetic and so reach the liver. Injury to the sympathetic ganglia 
is often followed by diabetes. Peripheral stimulation of various nerves, 
e. g ., sciatic, pneumogastric, depressor nerve, as well as the direct action of 
many drugs, impair or depress the hepatic vasomotor centre and so give 
rise to diabetes. 


SKIN. 

The Skin, the external investment of the body, is a most complex and 
important structure, serving (i) as a protective covering; (2) ag organ for 
tactile sensibility; (3) an organ for the elimination of excrementitious 
matters. 

The Amount of Skin investing the body of a man of average size is 
about twenty feet, and varies in thickness, in different situations, from the 
^ to the of an inch. 

The skin consists of two principal layers, viz., a deeper portion, the 
Corium , and a superficial portion, the Epidermis. 

The Corium, or Cutis Vera, may be subdivided into a reticulated and 
a papillary layer. The former is composed of white fibrous tissue, non- 
striated muscular fibres and elastic tissue, interwoven in every direction, 
forming an areolar network, in the meshes of which are deposited masses 
of fat, and a structureless amorphous matter; the latter is formed mainly of 
club shaped elevations or projections of the amorphous matter, constituting 
th t papillce; they are most abundant, and well developed, upon the palms 
of the hands and the soles of the feet; they average the of an inch 
in length, and may be simple or compound; they are well supplied with 
nerves, blood vessels and lymphatics. 

The Epidermis or Scarf Skin is an extra-vascular structure, a product 
of the true skin, and composed of several layers of cells. It may be 
divided into two layers, the rete mucosum or the Malpighian layer, and 
the horny or corneous. 

The former closely applies itself to the papillary layer of the true skin, 
and is composed of large, nucleated cells, the lowest layer of which, the 
“ prickle cells,” contain pigment granules, which give to the skm its varying 


APPENDAGES OF THE SKIN. 


89 


tints in different individuals and in different races of men ; the more super¬ 
ficial cells are large, colorless, and semi-transparent. The latter, the corne¬ 
ous layer, is composed of flattened cells, which, from their exposure to the 
atmosphere, are hard and horny in texture ; it varies in thickness from '/% 
of an inch on the palms of the hands and feet, to the g^.of an inch in the 
external auditory canal. 


APPENDAGES OF THE SKIN. 

Hairs are found in almost all portions of the body, and can be divided 
into (i) long, soft hairs, on the head; (2) short, stiff hairs, along the edges 
of the eyelids and nostrils; (3) soft, downy hairs, on the general cutaneous 
surface. They consist of a root and a shaft, which is oval in shape, and 
about the T fa of an inch in diameter; it consists of fibrous tissue, covered 
externally by a layer of imbricated cells, and internally by cells containing 
granular and pigment material. 

The Root of the hair is embedded in the hair follicle, formed by a tubular 
depression of the skin, extending nearly through to the subcutaneous tissue ; 
its walls are formed by the layers of the corium, covered by epidermic cells. 
At the bottom of the follicle is a papillary projection of amorphous matter, 
corresponding to a papillae of the true skin, containing blood vessels and 
nerves, upon which the hair root rests. The investments of the hair roots 
are formed of epithelial cells, constituting the internal and external root 
sheaths. 

The hair protects the head from the heat of the sun and cold, retains the 
heat of the body, prevents the entrance of foreign matter into the lungs, 
nose, ears, etc. The color is due to the pigment matter, which, in old age, 
becomes more or less whitened. 

The Sebaceous Glands, imbedded in the true skin, are simple and 
compound racemose glands, opening, by a common excretory duct, upon 
the surface of the epidermis or into the hair follicle. They are found in 
all portions of the body, most abundantly in the face, and are formed by a 
delicate, structureless membrane, lined by flattened polyhedral cells. The 
sebaceous glands secrete a peculiar oily matter, the sebum, by which the 
skin is lubricated and the hairs softened; it is quite abundant in the region 
of the nose and forehead, which often present a greasy, glistening appear¬ 
ance; it consists of water, mineral salts, fatty globules, and epithelial 
cells. 

The Vernix caseosa which frequently covers the surface of the foetus at 
G 


90 


HUMAN PHYSIOLOGY. 


birth consists of the residue of the sebaceous matters, containing epithelial 
cells and fatty matters; it seems to keep the skin soft and supple, and 
guards it from the effects of the long-continued action of water. 

The Sudoriparous Glands excrete the sweat; they consist of a mass 
or coil of a tubular gland duct, situated in the derma and in the subcuta¬ 
neous tissue; average the of an inch in diameter, and are surrounded by 
a rich plexus of capillary blood vessels. From this coil the duct passes in a 
straight direction up through the skin to the epidermis, where it makes a 
few spiral turns and opens obliquely upon the surface. The sweat glands 
consist of a delicate homogeneous membrane lined by epithelial cells, 
whose function is to extract from the blood the elements existing in the 
perspiration. 

The glands are very abundant all over the cutaneous surface, as many as 
3528 to the square inch, according to Erasmus Wilson. 

The Perspiration is an excrementitious fluid, clear, colorless, almost 
odorless, slightly acid in reaction, with a specific gravity of 1.003 or 1*004. 

The total quantity of perspiration excreted daily has been estimated at 
about two pounds, though the amount varies with the nature of the food 
and drink, exercise, external temperature, season, etc. 

The elimination of the sweat is not intermittent, but continuous; but it 
takes place so gradually that as fast as it is formed it passes off by evapora¬ 
tion as insensible perspiration. Under exposure to great heat and exercise 
the evaporation is not sufficiently rapid, and it appears as sensible perspira¬ 
tion. 


COMPOSITION OF SWEAT. 

Water,. 

Urea,. 

Fatty matters,. 

Alkaline lactates,. 

Alkaline sudorates,. 

Inorganic salts,. 


995-573 

0.043 

0.014 

0.317 

1.562 

2.491 


1000.00 

Urea is a constant ingredient. 

Carbonic acid is also exhaled from the skin, the amount being about 
of that from the lungs. 

Perspiration regulates the temperature, and removes waste matters from 
the blood; it is so important, that if elimination be prevented death occurs 
in a short time. 

Influence of the Nervous System. The secretion of sweat is regu¬ 
lated by the nervous system. Here, as in the secreting glands, the fluid is 









APPENDAGES OF THE SKIN. 


91 


formed from material in the lymph spaces surrounding the gland. Two 
sets of nerves are concerned, viz: vasomotor , regulating the blood supply; 
and secretory , stimulating the activities of the gland cells. Generally the 
two conditions, increased blood flow and increased glandular action, coexist. 
At times profuse clammy perspiration occurs, with diminished blood flow. 

The dominating sweat centre is located in the medulla, though subordi¬ 
nate centres are present in the cord. The secretory fibres reach the perspi¬ 
ratory glands of the head and face through the cervical sympathetic; of the 
arms, through the thoracic sympathetic, ulnar and radial nerves; of the leg, 
through the abdominal sympathetic and sciatic nerves. 

The sweat centre is excited to action by mental emotions, increased tem¬ 
perature of blood circulating in the medulla and cord, increased venosity 
of blood, and many drugs, rise of external temperature, exercise, etc. 



92 


HUMAN PHYSIOLOGY. 


NERVOUS SYSTEM. 

The Nervous System coordinates all the various organs and tissues 
of the body, and brings the individual into conscious relationship with 
external nature by means of sensation, motion, language, mental and moral 
manifestations. 

The Nervous Tissue may be divided into two systems, the Cerebro¬ 
spinal and the Sympathetic. 

(1) The Cerebro-spinal System, occupies the cavities of the cranium 
and spinal canal, and consists of the brain, the spinal cord, the cranial and 
spinal nerves. It is the system of animal life, and presides over the func¬ 
tions of sensation, motion, etc. 

(2) The Sympathetic System, situated along each side of the spinal 
column, consists (1) of a double chain of ganglia, united together by nerve 
cords, and extends from the base of the cranium to the coccyx ; (2) of various 
ganglia, situated in the head and face, thorax, abdomen, pelvis, etc. All 
the ganglia are united together by numerous communicating fibres, many 
of which anastomose with the fibres of the cerebro-spinal system. It is 
the nervous system of organic life, and governs the functions of nutrition, 
growth, etc. 

Nervous Tissue is composed of two kinds of matter, the gray and 
white , which differ in their color, structure and physiological endowments; 
the former consists of vesicles or cells which receive and generate nerve 
force; the latter consists of fibres which simply conduct it, either from the 
periphery to the centre or the reverse. 

Structure of Gray matter. The gray matter found on the surface of 
the brain in the convolutions, in the interior of the spinal cord, and in the 
various ganglia of the cerebro-spinal and sympathetic nervous systems, 
consists of a fine connective tissue stroma, the neuroglia , in the meshes of 
which are embedded the gray cells or vesicles. 

The cells are grayish in color, and consist of a delicate investing capsule 
containing a soft, granular, albuminous matter, a nucleus , and sometimes a 
nucleolus. Some of the cells are spherical or oval in shape, while others 
have an interrupted outline, on account of having one, two or more pro¬ 
cesses issuing from them, constituting the uni-polar , bi-polar or multi-polar 
nerve cells. Cells vary in size; the smallest being found in the brain, the 


. NERVOUS SYSTEM. 


93 


largest in the anterior horns of gray matter of the spinal cord. Some of 
the cell processes become continuous with the fibres of the white matter, 
while others anastomose with those of adjoining cells and form a plexus. 

Structure of the White Matter. The white matter, found for the 
most part in the interior of the brain, on the surface of the spinal cord, and 
in almost all the nerves of the cerebro-spinal and sympathetic systems, 
consists of minute tubules or fibres, the ultimate nerve filaments , which in 
the perfectly fresh condition, are apparently structureless and homogeneous; 
but when carefully examined after death are seen to consist of three distinct 
portions, (i) a tubular membrane; (2) the white substance of Schwann; 
(3) the axis cylinder. 

The Tubular membrane, investing the nerve filament, is thin, homoge¬ 
neous, and lined by large, oval nuclei, and presents, in its course, annular 
constrictions; it serves to keep the internal parts of the fibre in position, 
and protects them from injury. 

The White substance of Schwann, or the medullary layer , is situated 
immediately within the tubular membrane, and gives to the nerves their 
peculiar white and glistening appearance. It is composed of oleaginous 
matter in a more or less fluid condition; after death it undergoes coagula¬ 
tion, giving to the fibre a knotted or varicose appearance. It serves to 
insulate the axis cylinder, and prevents the diffusion of the nerve force. 

The Axis cylinder occupies the centre of the medullary substance. In 
the natural condition it is transparent and invisible, but when treated with 
proper reagents, it presents itself as a pale, granular, flattened band, albu¬ 
minous in character, more or less solid, and somewhat elastic. It is com¬ 
posed of a number of minute fibrillae united together to form a single 
bundle. (Schultze.) 

Nerve fibres in which these three structural elements coexist are known 
as the medullated nerve fibres. In the sympathetic system, and in the gray 
substance of the cerebro-spinal system, many nerves are destitute of a me¬ 
dullary layer, and are known as the non-medullated nerve fibres. 

Gray or Gelatinous nerve fibres, found principally in the sympathetic 
system, are gray in color, semi-transparent, flattened, with distinct borders, 
finely granular, and present oval nuclei. 

The diameter of the gelatinous fibres is about the of an inch; of 
the medullated fibres from jjoo to an inch- 

Ganglia are small bodies, varying considerably in size, situated on the 
posterior roots of spinal nerves, on the sensory cranial nerves, alongside of 
the vertebral column, forming a connecting chain, and in the different 


94 


HUMAN PHYSIOLOGY. 


viscera. They consist of a dense, investing, fibrous membrane, containing 
in its interior gray or vesicular cells, among which are found white and gela¬ 
tinous nerve fibres. They may be regarded as independent nerve centres. 

Structure of Nerves. Within the cranial and spinal cavities, the nerve 
fibres are bound together by connective tissue in the form of continuous 
bundles. Through the foramina of these cavities the nerve fibres emerge 
in the form of rounded or flattened cords which are termed nerves. Each 
nerve is surrounded by a sheath of connective tissue, the neurilemma , 
which also forms a stroma in which the blood vessels ramify, furnishing 
nutritive material for the growth and repair of the ultimate nerve fibres. 

A Nerve consists of a greater or less number of ultimate nerve filaments , 
separated into bundles by fibrous septa given off from the neurilemma. The 
nerve filaments pursue an uninterrupted course, from their origin to their 
termination; branches pass from one nerve trunk into the sheath of 
another, but there is no anastomosis or coalescence with adjoining nerve 
fibres. Nerves are channels of connection between the brain and cord, 
and the muscles, glands, skin, mucous membranes, etc., in which they ter¬ 
minate. Any excitation at either end produces in the nerve an impulse 
which travels throughout the length of the fibre. If the nerve fibres going 
to a muscle or gland are stimulated, there is increased muscular movement, 
and increased secretion; if the nerve fibres distributed to the skin or mucous 
membranes are stimulated, there is produced in the brain a sensation. This 
difference in effects produced by irritation has led to a division of fibres 
into two classes: viz., I. Efferent ox motor. 2. Afferent ox sensory. There 
is no anatomical or chemical difference discoverable between these two 
classes of fibres. 

A Plexus is formed by a number of branches of different nerves inter- 
lacing in every direction, in the most intricate manner, but from which 
fibres are again given off to pursue their independent course, e. g. t brachial, 
cervical, lumbar, sacral, cardiac plexuses, etc. 

Nerve Terminations. (1) Central. Both motor and sensory nerve 
fibres, as they enter the spinal cord and brain, lose their external invest¬ 
ments, and retaining only the axis cylinder, ultimately become connected 
with the processes of the gray cells. 

(2) Peripheral. As the nerves approach the tissues to which they are 
to be distributed, they inosculate freely, forming a plexus from which the 
ultimate fibres proceed to individual tissues. 

Motor Nerves. In the voluntary or striped muscles the motor nerves 
are connected with the contractile substance by means of the “ motorial 


PROPERTIES AND FUNCTIONS OF NERVES. 


95 


end plates when the nerve enters the muscular fibre the tubular mem¬ 
brane blends with the sarcolemma, the medullary layer disappears, and the 
axis cylinder spreads out into the form of a little plate, granular in charac¬ 
ter, and containing oval nuclei. 

In the unstriped or involuntary muscles, the terminal nerve fibres form 
a plexus on the muscular fibre cells, and become connected with the granu¬ 
lar contents of the nuclei. 

In the glands nerve fibres have been traced to the glandular cells, where 
they form a branching plexus from which fibres pass into their interior and 
become connected with their substance, and thus influence secretion. 

Sensitive Nerves terminate in the skin and mucous membranes, in 
three distinct modes, e.g., as tactile corpuscles, Pacinian corpuscles, and as 
end bulbs. 

The tactile corpuscles are found in the papillae of the true skin, especially 
on the palmar surface of the hands and fingers, feet and toes; they are 
oblong bodies, measuring about of an inch in length, consisting of a 
central bulb of homogeneous connective tissue surrounded by elastic fibres 
and elongated nuclei. The nerve fibre approaches the base of the corpus¬ 
cle, makes two or three spiral turns around it, and terminates in loops. 
They are connected with the sense of touch. 

The Pacinian corpuscles are found chiefly in the subcutaneous cellular 
tissue, on the nerves of the hands and feet, the intercostal nerves, the 
cutaneous nerves, and in many other situations. They are oval in shape, 
measure about the y 1 ^ of an inch in length on the average, and consist of 
concentric layers of connective tissue; the nerve fibre penetrates the cor¬ 
puscle and terminates in a rounded knob in the central bulb. Their function 
is unknown. 

The end bulbs of Krause are formed of a capsule of connective tissue in 
which the nerve fibre terminates in a coiled mass or bulbous extremity; 
they exist in the conjunctiva, tongue, glans penis, clitoris, etc. 

Many sensitive nerves terminate in the papillae at the base of the hair 
follicle; but in the skin, mucous membranes, and organs of special sense 
their mode of termination is not well understood. 


PROPERTIES AND FUNCTIONS OF NERVES. 

Classification. Nerves may be divided into two groups, viz. :— 

(i) Afferent ox centripetal,as when they convey to the nerve centres the 
impressions which are made upon their peripheral extremities or parts of 
their course. They may be sensitive, when they transmit impressions which 


96 


HUMAN PHYSIOLOGY. 


give rise to sensations; reflective or excitant , when the impression carried 
to the nerve centre is reflected outward by an efferent nerve and produces 
motion or some other effect in the part to which the nerve is distributed. 

(2) Efferent or centrifugal , as when the impulses generated in the centres 
are transmitted outward to the muscles and various organs. They may be 
motor , as when they convey impulses to the voluntary and involuntary 
muscles; vasomotor , when they regulate the calibre of the small blood 
vessels, increasing or diminishing the amount of blood to a part; secretory, 
when they influence secretion; trophic , when they influence nutrition; 
inhibitory , when they conduct impulses which produce a restraining or 
inhibiting action. 

Irritability , excitability , neurility. All nerves possess the property of 
being called into action by a stimulus in virtue of the possession of an 
ultimate and inherent property denominated irritability or excitability , 
which is manifested so long as the physical and chemical integrity of the 
nerve is maintained. During the period of excitement, no change in the 
nerve is appreciable except an electrical one. 

The irritability of a motor nerve is demonstrated by the contraction of 
the muscles to which it is distributed; the impulse aroused by an irritant 
travels outward to the muscles and calls forth a contraction. 

The irritability of a sensory nerve is demonstrated by the development 
of a conscious sensation. An irritation applied to a sensory nerve in any 
part of its course arouses an impulse which travels to the brain and produces 
there a sensation. The irritability of a sensory nerve may be increased by 
congestion or inflammation and decreased by cold, compression and injuries. 
Other tissues— e.g., muscles, glands, etc.—possess irritability, and when 
subjected to the action of a stimulus react in their own particular way. The 
irritability of nerves is distinct and independent of the irritability of muscles 
and glands, as can be demonstrated by the use of poisons, such as woorara, 
atropia, etc. 

The properties of sensation and motion reside in different nerve fibres. 
Motor nerves can be destroyed or paralyzed by the introduction of 
woorara under the skin, without affecting sensation ; the sensibility of 
nerves can be abolished by the employment of anaesthetics without destroy¬ 
ing motion. 

In the transmission of the nerve impulse the axis cylinder is the essential 
conducting agent, the white substance of Schwann and tubular membrane 
being probably accessory structures, protecting the axis frpm injury, and 
preventing the diffusion of nerve force to adjoining nerves. 

Nerve Degeneration. When nerves are separated from their trophic 


PROPERTIES AND FUNCTIONS OF NERVES. 


97 


or nutritive centres, they degenerate progressively in the direction in 
which they conduct impressions. In motor nerves, from the centre to the 
periphery; in sensory nerves, from the periphery to the centres. 

Stimuli of Nerves. Nerves do not possess the power of spontaneously 
generating and propagating nerve impulses; they can only be aroused to 
activity by the action of an extra-neural stimulus. In the living condition, 
the stimuli capable of throwing the nerve into an active condition act for 
the most part on either the central or peripheral end of the nerve. In the 
case of motor nerves the stimulus to the excitation, originating in some 
molecular disturbance in the nerve cells, acts upon the nerve fibres in con¬ 
nection with them. In the case of sensory or afferent nerves the stimuli act 
upon the peculiar end organs with which the sensory nerves are in connec¬ 
tion, which in turn excite the nerve fibres. Experimentally, it can be 
demonstrated that nerves can be excited by a sufficiently powerful stimulus 
applied in any part of their extent. 

Nerves respond to stimulation according to their habitual function; thus, 
stimulation of a sensory nerve, if sufficiently strong, results in the sensation 
of pain; of the optic nerve, in the sensation of light; of a motor nerve, in 
contraction of the muscle to which it is distributed; of a secretory nerve, 
in the activity of the related gland, etc. It is, therefore, evident that pecu¬ 
liarity of nervous function depends neither upon any special construction or 
activity of the nerve itself, nor upon the nature of the stimulus, but entirely 
upon the peculiarities of its central and peripheral end organs. 

Nerve stimuli may be divided into: 1st, General stimuli , comprising 
those agents which are capable of exciting a nerve in any part of its course; 
2d, Special stimuli, comprising those agents which act upon nerves only 
through the intermediation of the end organs. 

General stimuli :— 

1. Mechanical: as from a blow, pressure, tension, puncture, etc. 

2. Thermal: heating a nerve at first increases and then decreases its 

excitability. 

3. Chemical: Sensory nerves respond somewhat less promptly than motor 

nerves to this form of irritation. 

4. Electrical; Either the constant or interrupted current. 

5. The normal physiological stimulus:— 

(a) Centrifugal or afferent if proceeding from the centre toward the 
periphery. 

(£) Centripetal or afferent if in the reverse direction. 


98 


HUMAN PHYSIOLOGY. 


Special slbnuli :— 

1. Light or ethereal vibrations acting upon the end organs of the optic 

nerve in the retina. 

2. Sound or atmospheric undulations acting upon the end organs of the 

auditory nerve. 

3. Heat or vibrations of the air acting upon the end organs in the skin. 

4. Chemical agencies acting upon the end organs of the olfactory and 

gustatory nerves. 

As to the nature of the nerve impulse generated by the above stimuli but 
little is known. It is supposed to be a mode of motion, molecular or 
vibratory in character, which passes through the axis cylinder with a definite 
velocity. 

Rapidity of Transmission of Nerve Force. The passage of a nervous 
impulse, either from the brain to the periphery or in the reverse direction, 
requires an appreciable period of time. The velocity with which the 
impulse travels in human sensory nerves has been estimated at about 190 
feet per second, and for motor nerves at from 100 to 200 feet per second. 
The rate of movement is, however, somewhat modified by temperature, cold 
lessening and heat increasing the rapidity; it is also mqdified by electrical 
conditions, by the action of drugs, the strength of the stimulus, etc. The 
rate of transmission through the spinal cord is considerably slower than in 
nerves, the average velocity for voluntary motor impulses being only 33 
feet per second, for sensitive impressions 40 feet, and for tactile impressions 
140 feet per second. 

Phenomena of Muscles and Nerves. The muscles are the motor 
organs of the body and constitute a large per cent, of the body weight. 
Muscles are of two kinds, striated and non-striated or involuntary. The 
striated muscles consist of bundles of fibres, the fasciculi , held together by 
connective tissue. Each muscle fibre is about ]/ z to 1% inches long, and 
possesses a delicate homogeneous membrane, the sarcolemma , in the interior 
of which is contained the contractile substance, which presents a striated 
appearance. During life this substance is in a fluid condition, but after 
death undergoes stiffening. 

The non-striated muscles form membranes which surround cavities, e.c., 

7 o j 

stomach, arteries, bladder, etc. They are composed of elongated cells 
without striations, and contain in their interior one or more nuclei. 

Muscular tissue is composed of water, an organic contractile substance, 
myosin, non-nitrogenized substances, such as glycogen, inosite, fat, and 


PROPERTIES AND FUNCTIONS OF NERVES. 


99 


inorganic salts. When at rest the muscle is alkaline in reaction, but during 
and after contraction it becomes acid. 

Muscles possess the properties of (i) Contractility, which is the capa¬ 
bility of shortening themselves in the direction of their long axis, and at 
the same time becoming thicker and more rigid. (2) Extensibility , by 
means of which they are lengthened in proportion to weights attached. 
(3) Elasticity , in virtue of which they return to their original shape when 
the force applied is removed. 

The contractility of muscles is called forth mainly by nervous impulses, 
descending motor nerves, which originate in the central nervous system; 
but it can also be excited by the electric current, the application of strong 
acids, heat, or by mechanical means. 

Phenomena of a Muscular Contraction. When a single induction 
shock is propagated through a nerve, the muscle to which it is distributed 
undergoes a quick pulsation, and speedily returns to its former condition. 
As is shown by the muscle curve, the contraction, which is at first slow, 
increases in rapidity to its maximum, gradually relaxes and is again at rest, 
the entire pulsation not occupying more than the 0 f a second. 

The muscular contraction does not instantly follow the induction shock, 
even when the electrodes are placed directly upon the muscular fibres 
themselves; an appreciable period intervenes before the contraction, during 
which certain chemical changes are taking place preparatory to the mani¬ 
festation of force. This is the “ latent period,” which has an average dura¬ 
tion of the of a second, but varies with the temperature, the strength 
of the stimulus, the animal, etc. The muscular movements of the body, 
however, are occasioned by contractions of a much longer duration, depend¬ 
ing upon the number (the average, 20) of nervous impulses passing to the 
muscles in a second. 

During the muscular contraction the following phenomena are observed, 
viz.: a change in form, a rise in temperature, a consumption of oxygen and 
an evolution of carbonic acid; the production of a distinct musical sound, 
a change from an alkaline to an acid reaction, from the development of 
sarcolactic acid; a disappearance of the natural muscle currents, which 
under a negative variation in the “latent period,” just after the nervous 
impulse reaches the termination of the nerve, and before the appearance 
of the muscular contraction wave. 

Electrical Currents in Muscles and Nerves. If a muscle or nerve 
be divided and non-polarizable electrodes be placed upon the natural 
longitudinal surface at the equator, and upon the transverse section, electri- 


100 


HUMAN PHYSIOLOGY. 


cal currents are observed with the aid of a delicate galvanometer. The 
direction of the current is always from the positive equatorial surface to the 
negative transverse surface. The strength of the current increases or dimin¬ 
ishes according as the positive electrode is moved toward or from the 
equator. When the electrodes are placed on the two transverse ends of a 
nerve, an axial current will be observed whose direction is opposite to that 
of the normal impulse in the nerve. 

The electromotive force of the strongest nerve current has been estimated 
to be equal to the 0.026 of a Daniell battery; the force of the current of the 
frog muscle about 0.05 to 0.08 of a Daniell. 

Negative Variation of Currents in Muscles and Nerves. If a 
muscle or nerve be thrown into a condition of tetanus, it will be observed that 
the currents undergo a diminution or negative variation, a change which 
passes along the nerve in the form of a wave and with a velocity equal to 
the rate of transmission of the nerve impulse. The wave length of a single 
negative variation has been estimated to be 18 millimetres; the period of 
its duration being from 0.0005 to 0.0008 of a second. 

It is asserted by Hermann that perfectly fresh, uninjured muscles and 
nerves are devoid of currents, and that the currents observed are the result 
of a molecular death at the point of section, this point becoming negative 
to the equatorial point. He applies the term “ action currents ” to the cur¬ 
rents obtained when a muscle is thrown into a state of activity. 

Electrical Properties of Nerves. When a galvanic current is made 
to flow along a motor nerve from the centre to the periphery, from the 
positive to the negative pole, it is known as the direct , descending or centri¬ 
fugal current. When it is made to flow in the reverse direction it is known 
as the inverse , ascending or centripetal current. 

The passage of a direct current enfeebles the excitability of a nerve; the 
passage of the inverse current increases it. The excitability of a nerve may 
be exhausted by the repeated applications of electricity; when thus 
exhausted it may be restored by repose, or by the passage of the inverse 
current if the nerve has been exhausted by the direct current or vice versa. 

During the actual passage of a feeble constant current in either direction 
neither pain nor muscular contraction is ordinarily manifested ; if the current 
be very intense the nerve may be disorganized and its excitability destroyed. 

Electrotonus. The passage of a direct galvanic current through a por¬ 
tion of a nerve excites in the parts beyond the electrodes a condition of 
electric tension or electrotonus , during which the excitability of the nerve 
is decreased near the anode or positive pole, and increased near the kathode 


PROPERTIES AND FUNCTIONS OF NERVES. 


101 


or negative pole; the increase of excitability in the kateledrotonic area , 
that nearest the muscle, being manifested by a more marked contraction of 
the muscle than the normal, when the nerve is irritated in this region. The 
passage of an inverse galvanic current excites the same condition of 
electrotonus; and the diminution of excitability near the anode, the anelec- 
trotonic area , that now nearest the muscle, being manifested by a less 
marked contraction than the normal when the nerve is stimulated in this 
region. Between the electrodes is a neutral point where the katelectrotonic 
area emerges into the anelectrotonic area. If the current be a strong one, 
the neutral point approaches the kathode; if weak, it approaches the 
anode. 

When a nervous impulse passes along a nerve, the only appreciable effect 
is a change in its electrical condition, there being no change in its tempera¬ 
ture, chemical composition or physical condition. The natural nerve cur¬ 
rents, which are always present in a living nerve as a result of its nutritive 
activity, in great part disappear during the passage of an impulse, under¬ 
going a negative variation. 

Law of Contraction. If a feeble galvanic current be applied to a recent 
and excitable nerve, contraction is produced in the muscles only upon the 
making of the circuit with both the direct and inverse currents. 

If the current be moderate in intensity, the contraction is produced in the 
muscle both upon the making and breaking of the circuit, with both the 
direct and inverse currents. 

If the current be intense , contraction is produced only when the circuit 
is made with the direct current, and only when it is broken with the inverse 
current. 

The Reaction of Degeneration. Two different applications of elec¬ 
tricity are used in electro-physiology and electro-therapeutics—the constant 
or galvanic, and the interrupted or faradic currents. Injured and paralyzed 
muscles and nerves react differently to these two kinds of stimuli, and the 
facts are of the greatest importance in the diagnosis and therapeutics of the 
precedent lesions. The principal difference of behavior relates to the 
reaction of degeneration —a condition produced by paralysis of any kind. 
It is characterized by a diminished or abolished excitability of the muscles 
to the faradic current, while there is at the same time an increased excita¬ 
bility to the galvanic current. The synchronous diminished excitability of 
the nerves is the same for either current. The term partial reaction of 
degeneration is used when there is a normal reaction of the nerves, but the 
muscles show the degenerative reaction. This condition is a characteristic 
of progressive muscular atrophy. 


02 


HUMAN PHYSIOLOGY. 


CRANIAL NERVES. 


The Cranial Nerves come off from the base of the brain, pass through 
the foramina in the walls of the cranium, and are distributed to the skin, 


muscles and organs of sense in the face and head. 

According to the classification of Soemmering, there are 12 pairs of 
nerves, enumerating them from before backward, as follows, viz :— 


1st Pair, or Olfactory. 

2d Pair, or Optic 

3d Pair, or Motor oculi communis. 
4th Pair, or Patheticus, Trochlearis, 
5th Pair, or Trifacial, Trigeminus. 
6th Pair, or Abducens. 


7th Pair, or Facial, Portio dura. 

8th Pair, or Auditory, Portio mollis. 
9th Pair, or Glosso-pharyngeal. 

10th Pair, or Pneumogastric. 
nth Pair, or Spinal accessory. 

12th Pair, or Hypoglossal. 


The Cranial Nerves may also be classified physiologically, according 
to their function, into three groups : 1. Nerves of special sense. 2. Nerves 
of motion. 3. Nerves of general sensibility. 


1st Pair. Olfactory. 

Apparent Origin. From the inferior and internal portion of the ante¬ 
rior lobes of the cerebrum by three roots, viz: an external white root , which 
passes across the fissure of Sylvius to the middle lobe of the cerebrum ; an 
* internal white root , from the most posterior part of the anterior lobe; a ,gray 
root, from the gray matter in the posterior and inner portion of the inferior 
surface of the anterior lobe. 

Deep Origin. Not satisfactorily determined. 

Distribution. The olfactory nerve, formed by the union of the three 
roots, passes forward along the under surface of the anterior lobe to the 
ethmoid bone, where it expands into the olfactory bulb. This bulb con¬ 
tains ganglionic cells, is grayish in color and soft in consistence; it gives off 
from its under surface from fifteen to twenty nerve filaments, the true 
olfactory nerves , which pass through the cribriform plate of the ethmoid 
bone, and are distributed to the Schneiderian mucous membrane. This 
membrane extends from the cribriform plate of the ethmoid bone downward, 
about one inch. 

Properties. The olfactory nerves give rise to neither motor nor sensory 
phenomena when stimulated. They carry simply the special impressions 
of odorous substances. Destruction or injury of the olfactory bulbs is 
attended by a loss of the sense of smell. 

Function. Governs the sense of smell. Conducts the impressions which 
give rise to odorous sensations. 


CRANIAL NERVES. 


103 


2d Pair. Optic. 

Apparent Origin. From the anterior portion of the optic commissure. 

Deep Origin. The origins and connections of the optic tract are very 
complex. The immediate origins are bands of fibres from the thalamus 
opticus and anterior corpora quadrigemina. The corpora geniculata are 
interposed ganglia. The ultimate roots are traced— 

1. By a broad band of fibres—“ the optic radiation of Gratiolet ”—to the 

psycho-optic centres in the occipital lobes. 

2. To the gyrus hippocampi and sphenoidal lobes. 

3,. Through the corpus callosum to the motor areas of the opposite cere¬ 
bral hemispheres. 

4. To the frontal region by “ Meynert’s Commissure.” 

5. To the spinal cord. 

6. To the corpora geniculata, pulvinar, and anterior corpora geniculata by 

ganglionic roots. 

Distribution. The two roots unite to form a flattened band, the optic 
tract, which winds around the crus cerebri to decussate with the nerve of 
the opposite side, forming the optic chiasm. The decussation of fibres is 
not complete ; some of the fibres of the left optic tract going to the outer 
half of the eye of the same side, and to the inner half of the eye of the 
opposite side; the same holds true for the right optic tract. 

The optic nerves proper arise from the commissure, pass forward through 
the optic foramina, and are finally distributed in the retince. 

Properties. They are insensible to ordinary impressions, and convey 
only the special impressions of light. Division of one of the nerves is 
attended by complete blindness in the eye of the corresponding side. 

Hemiopia and Hemianopsia. Owing to the decussation of the fibres 
in the optic chiasm division of the optic tract produces loss of sight in 
the outer half of the eye of the same side, and in the inner half of the 
eye of the opposite side, the blind part being separated from the normal part 
by a vertical line. The term hemiopia is applied to the loss of function or 
paralysis of the one-half of the retina; hemianopsia is applied to the blind¬ 
ness in the field of vision. If, for example, the right optic tract be divided, 
l here will be hemiopia in the outer half of the right eye and inner half of 
left eye, thus causing left lateral hemianopsia , and as the two halves are 
affected which correspond in normal vision, it is spoken of as homonymous 
hemianopsia. Lesion of the anterior part of the optic chiasm causes blind¬ 
ness in the inner half of the two eyes. 


104 


HUMAN PHYSIOLOGY. 


Functions. Governs the sense of sight. Receives and conveys to the 
brain the luminous impressions which give rise to the sensation of sight. 

The reflex movements of the iris are called forth by the optic nerve. 
When an excess of light falls upon the retina the impression is carried 
back to the tubercula quadrigemina, where it is transformed into a motor 
impulse, which then passes outward through the motor oculi nerve to the 
contractile fibres of the iris and diminishes the size of the pupil. The 
absence of light is followed by a dilatation of the pupil. 

3d Pair. Motor Oculi Communis. 

Apparent Origin. From the inner surface of the crura cerebri. 

Deep Origin. By three sets of filaments coming from the oculo-motorius 
nucleus, which lies under the aqueduct of Sylvius; these three groups of 
filaments are destined for the innervation of the muscles of the eyeball, the 
sphincter pupillse, and the ciliary muscle. By filaments coming from the 
lenticular nucleus, corpora quadrigemina, optic thalamus; these filaments 
converge to form a main trunk, which winds around the crus cerebri, in 
front of the pons Varolii. 

Distribution. The nerve then passes forward, and enters the orbit 
through the sphenoidal fissure, where it divides into a superior branch 
distributed to the superior rectus and levator palpebrce muscles ; an inferior 
branch sending branches to the internal and inferior recti, and the inferior 
oblique muscles; filaments also pass into the ciliary or ophthalmic ganglion; 
from this ganglion the ciliary nerves arise which enter the eyeball, and are 
distributed to the circular fibres of the iris and the ciliary muscle. The 
3d nerve also receives filaments from the cavernous plexus of the sympa¬ 
thetic and from the fifth nerve. 

Properties. Irritation of the root of the nerve produces contraction 
of the pupil, internal strabismus, muscular movements of eye, but no pain. 
Division of the nerve is followed by ptosis (falling of the upper eyelid), 
external strabismus, due to the unopposed action of the external rectus 
muscle; paralysis of the accommodation of the eye; dilatation of the 
pupil from paralysis of the circular fibres of the iris and ciliary muscle; 
and inability to rotate the eye, slight protrusion and double vision. The 
images are crossed; that of the paralyzed eye is a little above that of the 
sound, and its upper end inclined toward it. 

Function. Governs movements of the eyeball by animating all the 
muscles except the external rectus and superior oblique, the movements of 


CRANIAL NERVES. 


105 


the iris, elevates the upper lid, influences the accommodation of the eye 
for distances. Can be called into action by (i) voluntary stimuli, (2) by 
reflex action through irritation of the optic nerve. 


4th Pair. Patheticus. 

Apparent Origin. From the superior peduncles of the cerebellum. 

Deep Origin. By fibres terminating in the corpora quadrigemina, 
lenticular nucleus, valve of Vieussens, and in the substance of the cere¬ 
bellar peduncles; some filaments pass over the median line and decussate 
with fibres of the opposite side. 

Distribution. The nerve enters the orbital cavity through the sphe¬ 
noidal fissure, and is distributed to the superior oblique muscle; in its 
course receives filaments from the ophthalmic branch of the 5th pair and the 
sympathetic. 

Properties. When the nerve is irritated muscular movements are pro¬ 
duced in the superior oblique muscle, and the pupil of the eye is turned 
downward and outward. Division or paralysis lessens the movements 
and rotation of the globe downward and outward. The diplopia conse¬ 
quent upon this paralysis is homonymous, one image appearing above the 
other. The image of the paralyzed eye is below, its upper end inclined 
toward that of the sound eye. 

Function. Governs the movements of the eyeball produced by the 
action of the superior oblique muscles. 

6th Pair.* Abducens. Motor Oculi Externus. 

Apparent Origin. From the groove between the anterior pyramidal 
body and the pons Varolii, where it arises by two roots. 

Deep Origin. From the gray matter o'f the medulla oblongata. 

Distribution. The nerve then passes into the orbit through the sphe¬ 
noidal fissure, and is distributed to the external rectus muscle. Receives 
filaments from the cervical portion of the sympathetic, through the carotid 
plexus and spheno-palatine ganglion. 

Properties. When irritated , the external rectus muscle is thrown into 
convulsive movements, and the eyeball is turned outward. When divided 


* The 6th nerve is considered in connection with the 3d and 4th nerves, since they 
together constitute the motor apparatus by which the ocular muscles are excited to 
action. 

H 



106 


HUMAN PHYSIOLOGY. 


or paralyzed , this muscle is paralyzed; motion of the eyeball outward past 
the median line is impossible, and the homonymous diplopia increases as 
the object is moved outward past this line. The images are upon the same 
plane and parallel. Internal strabismus results because of the unopposed 
action of the internal rectus. 

Function. To turn the eyeball outward. 

5th Pair. Trifacial. Trigeminal. 

Apparent Origin. By two roots from the side of the pons Varolli. 

Deep Origin. The deep origin of the two roots is the upper part of 
the floor and anterior wall of the 4th ventricle, by three bundles of fila¬ 
ments, one of which anastomoses with the auditory nerve; another passes 
to the lateral tract of the medulla; while a third, grayish in color, goes to 
the restiform bodies, and may be traced to the point of the calamus scrip- 
torius. 

Filaments of origin have been traced to the “ trigeminal sensory nucleus,” 
located on a level with the point of exit of the nerve, and to the posterior 
gray horns of the cord, as low down as the middle of the neck. 

Distribution. The large root of the nerve passes obliquely upward 
and forward to the ganglion of Gasser, which receives filaments of com¬ 
munication from the carotid plexus of the sympathetic. It then divides into 
three branches. 

1. Ophthalmic branch , which receives communicating filaments from 
the sympathetic, and sends sensitive fibres to all the motor nerves of the 
eyeball. It is distributed to the ciliary ganglion, lachrymal gland, sac and 
caruncle, conjunctiva, integument of the upper eyelid, forehead, side of 
head and nose, anterior portion of the scalp, ciliary muscle and iris. 

2. Superior maxillary branch , sends branches to the spheno-palatine 
ganglion, integument of the teftiple and lower eyelid, side of forehead, 
nose, cheek and upper lip, teeth of the upper jaw, and alveolar processes. 

3. Inferior maxillary branch , which, after receiving in its course fila¬ 
ments from the small root and from the facial, is distributed to the sub¬ 
maxillary ganglion, the parotid and sub-lingual glands, external auditory 
meatus, mucous membrane of the mouth, anterior two-thirds of the tongue 
(lingual branch), gums, arches of the palate, teeth of the lower jaw, 
and integument of the lower part of the face, and to the muscles of 
mastication. 

The small root passes forward beneath the ganglion of Gasser, through 
the foramen ovale, and joins the inferior maxillary division*of the large 


CRANIAL NERVES. 107 

root, which then divides into an anterior and posterior branch, the former 
of which is distributed to the muscles of mastication, viz.: temporal, mas- 
seter, internal and external pterygoid muscles. 

Properties. It is the most acutely sensitive nerve in the body, and 
endows all the parts to which it is distributed with general sensibility. 

Irritation of the large root , or any of its branches, will give rise to 
marked evidence of pain; the various forms of neuralgia of the head and 
face being occasioned by compression, disease, or exposure of some of its 
terminal branches. 

Division of the large root within the cranium is followed at once by a 
complete abolition of all sensibility in the head and face, but is not attended 
by any loss of motion. The integument, mucous membranes and the eye 
may be lacerated, cut or bruised, without the animal exhibiting any evidence 
of pain. At the same time the lachrymal secretion is diminished, the pupil 
becomes contracted, the eyeball is protruded, and the sensibility of the 
tongue is abolished. 

The reflex movements of deglutition are also somewhat impaired; the 
impression of the food being unable to reach and excite the nerve centre in 
the medulla oblongata. 

Galvanization of the small root produces movements of the muscles of 
mastication; section of the root causes paralysis of these muscles, and the 
jaw is drawn to the opposite side, by the action of the opposing muscles. 

Influence upon the Special Senses. After division of the large root 
within the cranium, a disturbance in the nutrition of the special senses 
sooner or later manifests itself. 

Sight. In the course of twenty-four hours the eye becomes very vascular 
and inflamed, the cornea becomes opaque and ulcerates, the humors are 
discharged, and the eye is totally destroyed. 

Si?iell. The nasal mucous membrane swells up, becomes fungous, and 
is liable to bleed on the slightest irritation. The mucus is increased in 
amount, so as to obstruct the nasal passages ; the sense of smell is finally 
abolished. 

Hearing. At times the hearing is impaired, from disorders of nutrition 
in the middle ear and external auditory meatus. 

Alteration in the nutrition of the special senses is not marked if the sec¬ 
tion is made posterior to the ganglion of Gasser, and to the anastomosing 
filaments of the sympathetic which join the nerve at this point; but if the 
ganglion be divided, these effects are very noticeable, due to the section of 
the sympathetic filaments. 


108 


HUMAN. PHYSIOLOGY. 


Function. Gives sensibility to all parts of the head and face to which 
it is distributed; through the small root endows the masticatory muscles 
with motion; through fibres from the sympathetic governs the nutrition of 
the special senses. 

7th Pair. Portio Dura. Facial Nerve. 

Apparent Origin. From the groove between the olivary and restiform 
bodies at the lateral portion of the medulla oblongata, and below the margin 
of the pons Varolii. 

Deep Origin. From a nucleus of large cells in the floor of the 4th 
ventricle, below the nucleus of origin of the 6th pair, with which it is 
connected. Some filaments are traceable to the lenticular nucleus of the 
opposite side. Some of the fibres cross the median line and decussate. It 
is intimately associated with the nerve of Wrisberg at its origin. 

Distribution. From its origin the facial nerve passes into the internal 
auditory meatus, and then, in company with the nerve of Wrisberg, enters 
the aqueduct of Fallopius. The filaments of the nerve of Wrisberg are 
supplied with a ganglion, of a reddish color, having nerve cells. These 
filaments unite with those of the root of the facial, to form a common trunk, 
which emerges at the stylo-mastoid foramen. 

In the aqueduct the facial gives off the following branches, viz.:— 

1. Large petrosal nerve , which passes forward to the spheno-palatine, or 
Meckel’s ganglion, and through this to the levator palati and azygos uvulae 
muscles, which receive motor influence from this source. 

2. Small petrosal nerve , passing to the otic ganglion and thence to the 
tensor-tympani muscle, endowing it with motion. 

3. Tympanic branch , giving motion to the stapedius muscle. 

4. Chorda tympani nerve, which after entering the posterior part of the 
tympanic cavity, passes forward between the malleus and incus bones, 
through the Glasserian fissure, and joins the lingual branch of the 5th 
nerve. It is then distributed to the mucous membrane of the anterior 
two-thirds of the tongue and the sub-maxillary glands. 

After emerging from the stylo-mastoid foramen, the facial nerve sends 
branches to the muscles of the ear, the occipito-frontalis, the digastric, the 
palato-glossi, and palato-pharyngei; after which it passes through the parotid 
gland and divides into the temporo-facial and cervico facial branches, which 
are distributed to the superficial muscles of the face, viz.; occipito-frontalis, 
corrugator supercilii, orbicularis palpebrarum, levator labii superioris et 
alseque nasi, buccinator, levator anguli oris, orbicularis oris, zygomatici, 
depressor anguli oris, platysma myoides, etc. 


CRANIAL NERVES. 109 

Properties. Undoubtedly a motor nerve at its origin, but in its course 
receives sensitive filaments from the 5th pair and the pneumogastric. 

Irritation of the nerve, after its emergence from the stylo-mastoid fora¬ 
men, produces convulsive movements in all the superficial muscles of the 
face. Division of the nerve at this point causes paralysis of these muscles 
on the side of the section, constituting facial paralysis; the phenomena of 
which are, a relaxed and immobile condition of the same side of the face; 
the eyelids remain open, from paralysis of the orbicularis palpebrarum ; 
the act of winking is abolished; the angle of the mouth droops, and saliva 
constantly drains away; the face is drawn over to the sound side; the face 
becomes distorted upon talking or laughing; mastication is interfered with, 
the food accumulating between the gums and cheek, from paralysis of the 
buccinator muscle; fluids escape from the mouth in drinking; articulation 
is impaired, the labial sounds being imperfectly pronounced. 

Properties of the branches given off in the aqueduct of Fallopius. The 
Large petrosal, when irritated, throws the levator palati and azygos uvulae 
muscles into contraction. Paralysis of this nerve, from deep-seated lesions, 
produces a deviation of the uvula to the sound side, a drooping of the palate, 
and an inability to elevate it. 

The Small petrosal influences hearing by animating the tensor tympani 
muscle; when paralyzed, there occurs partial deafness and an increased 
sensibility to sonorous impressions. 

The Tympanitic branch animates the stapedius muscle, and influences 
audition. 

The Chorda tympani influences the circulation and the secretion of 
saliva, in the sub-maxillary glands, and governs the sense of taste in the 
anterior two-thirds of the tongue. Galvanization of the chorda tympani 
dilates the blood vessels, increases the quantity and rapidity of the stream 
of blood, and increases the secretion of saliva. Division of the nerve is 
followed by contraction of the vessels, an arrestation of the secretion, and 
a diminution of the sense of taste, on the same side. 

Function. The facial is the nerve of expression, and coordinates the 
muscles employed to delineate the various emotions, influences the sense 
of taste, deglutition, movements of the uvula and soft palate, the tension of 
the membrana tympani, and the secretions of the sub-maxillary and parotid 
glands. Indirectly influences smell, hearing and vision. 

8 th Pair. Portio Mollis. Auditory Nerve. 

Apparent Origin. From the upper and lateral portion of the medulla 
oblongata, just below the margin of the pons Varolii. 


110 


HUMAN PHYSIOLOGY. 


Deep Origin. By two roots from the floor of the 4th ventricle, each 
root consisting of a number of gray filaments, some of which decussate in 
the median line; the external root has a gangliform enlargement contain¬ 
ing fusiform nerve cells. 

Distribution. The two roots wind around the restiform bodies and 
enter the internal auditory meatus, and divide into an anterior branch 
distributed to the cochlea, and a posterior branch distributed to the vesti¬ 
bule and semicircular canals. 

Properties. They are soft in consistence, grayish in color, consisting 
of axis cylinders with a medullary sheath only; they are not sensible to 
ordinary impressions, but convey the impression of sound. 

Function. Governs the sense of hearing. Receives and conducts to 
the brain the impression of sound, which gives rise to the sensations of 
hearing. 

9th Pair. Glosso-pharyngeal. 

Apparent Origin. Partly from the medulla oblongata and the inferior 
peduncles of the cerebellum. 

Deep Origin. From the lower portion of the gray substance in the 
floor of the 4th ventricle. 

This nerve has two ganglia; the jugular ganglion includes only a por¬ 
tion of the root filaments; the ganglion of Andersch includes all the fibres 
of the trunk. 

Distribution. The trunk of the nerve passes downward and forward, 
receiving near the ganglion of Andersch fibres from the facial and pneu- 
mogastric nerves. It divides into two large branches, one of which is 
distributed to the base of the tongue, the other to the pharynx. In its 
course it sends filaments to the otic ganglion; a tympanic branch which 
gives sensibility to the mucous membrane of the fenestra rotunda, fenestra 
ovalis, and Eustachian tube; lingual branches to the base of the tongue; 
palatal branches to the soft palate, uvula and tonsils; pharyngeal branches 
to the mucous membrane of the pharynx. 

Properties. Irritation of the roots at their origin calls forth evidences 
of pain ; it is, therefore, a sensory nerve, but its sensibility is not so acute 
as that of the trifacial. Irritation of the trunk after its exit from the 
cranium produces contraction of the muscles of the palate and pharynx, 
due to the presence of anastomosing motor fibres. 

Division of the nerve abolishes sensibility in the structures to which it is 
distributed, and impairs the sense of taste in the posterior third of the 
tongue (see Sense of Taste). 


CRANIAL NERVES. 


Ill 


Function. Governs sensibility of pharynx, presides partly over the 
sense of taste, and controls reflex movements of deglutition and vomiting. 

ioth Pair. Pneumogastric. Par Vagum. 

Apparent Origin. From the lateral side of the medulla oblongata, 
just behind the olivary body. 

Deep Origin. In the gray nuclei in the lower half of the floor of the 
4th ventricle, and in the substance of the restiform body. Some filaments 
are traced along the restiform tract, toward the cerebellum, and others to the 
median line of the floor of the 4th ventricle, where many of them decussate. 

This nerve has two ganglia; one in the jugular foramen, called the gan¬ 
glion of the root, and another outside of the cranial cavity on the trunk, 
the ganglion of the trunk. 

Distribution. The filaments from the root unite to form a single trunk, 
which leaves the cavity of the cranium, through the jugular foramen, in 
company with the spinal accessory and glosso-pharyngeal. It soon receives 
an anastomotic branch from the spinal accessory , and afterward branches 
from the facial, the hypoglossal and the anterior branches of the two upper 
cervical nerves. 

As the nerve passes down the neck it sends off the following main 
branches:— 

1. Pharyngeal nerves , which assist in forming the pharyngeal plexus, 
which is distributed to the mucous membrane and muscles of the pharynx. 

2. Superior laryngeal nerve , which enters the larynx through the thyro¬ 
hyoid membrane, and is distributed to the mucous membrane lining the 
interior of the larynx, and to the crico-thyroid muscle and the inferior con¬ 
strictor of the pharynx. The “ depressor nerve” found in the rabbit, is 
formed by the union of two branches, one from the superior laryngeal, the 
other from the main trunk; it passes downward to be distributed to the 
heart. 

3. Inferior laryngeal , which sends its ultimate branches to all the 
intrinsic muscles of the larynx except the crico-thyroid, and to the inferior 
constrictor of the pharynx. 

4. Cardiac branches given off from the nerve throughout its course, which 
unite with the sympathetic fibres to form the cardiac plexus, to be distributed 
to the heart. 

5. Pulmonary branches , which form a plexus of nerves and are dis¬ 
tributed to the bronchi and their ultimate terminations, the lobules and air 
cells. 


112 


HUMAN PHYSIOLOGY. 


From the right pneumogastric nerve branches are distributed to the 
mucous membrane and muscular coats of the stomach and intestines, to the 
liver, spleen, kidneys, and supra-renal capsules. 

Properties. At its otfgin the pneumogastric nerve is sensory, as shown 
by direct irritation or galvanization, though its sensibility is not very 
marked. In its course exhibits motor properties, from anastomosis with 
motor nerves. 

The Pharyngeal branches assist in giving sensibility to the mucous 
membrane of the pharynx, and influence reflex phenomena of deglutition 
through motor fibres which they contain, derived from the spinal 
accessory. 

The Superior laryngeal nerve endows the upper portion of the larynx 
with sensibility; protects it from the entrance of foreign bodies; by con¬ 
ducting impressions to the medulla, excites the reflex movements of deglu¬ 
tition and respiration; through the motor filaments it contains produces 
contraction of the crico-thyroid muscle. 

Division of the “ Depressor nerve” and galvanization of the central 
end, retards and even arrests the pulsations of the heart, and by depressing 
the vasomotor centre diminishes the pressure of blood in the large vessels, 
by causing dilatation of the intestinal vessels through the splanchnic 
nerves. 

The Inferior laryngeal contains, for the most part, motor fibres from 
the spinal accessory. When irritated produces movement in the laryn¬ 
geal muscles. When divided , is followed by paralysis of these muscles, 
except the crico-thyroid, impairment of phonation, and an embarrassment 
of the respiratory movements of the larynx, and finally death, from suffo¬ 
cation. 

The Cardiac branches , through filaments derived from the spinal acces¬ 
sory, exert a direct inhibitory action upon the heart. Division of the 
pneumogastrics in the neck increases the frequency of the heart’s action. 
Galvanization of the peripheral ends diminishes the heart’s pulsation, and, 
if sufficiently powerful, paralyzes it in diastole. 

The Pulmonary branches give sensibility to the bronchial mucous 
membrane, and govern the movements of respiration. Division of both 
pneumogastrics in the neck diminishes the frequency of the respiratory 
movements, falling as low as four to six per minute; death usually occurs 
in from five to eight days. Feeble galvanization of the central ends of the 
divided nerves accelerates respiration; powerful galvanization retards, and 
may even arrest the respiratory movements. 

The Gastric branches give sensibility to the mucous coat, and through 


CRANIAL NERVES. 


113 


sympathetic filaments, which join the pneumogastrics high up in the neck, 
give motion to the muscular coat of the stomach. They influence the 
secretion of gastric juice, aid the process of digestion and absorption from 
the stomach. 

The Hepatic branches , probably through anastomosing sympathetic fila¬ 
ments, influence the secretion of bile, and the glycogenic function of the 
liver; division of the pneumogastrics in the neck produces congestion of 
the liver, diminishes the density of the bile, and arrests the glycogenic 
function; galvanization of the central ends exaggerates the glycogenic 
function, and makes the animal diabetic. 

The Intestinal branches give sensibility and motion to the small intes¬ 
tines, and when divided, purgatives generally fail to produce purgation. 

Function. A great sensitive nerve, which, through anastomotic fila¬ 
ments from motor sources, influences deglutition, the action of the heart, 
the circulatory and respiratory systems, voice, the secretions of the stomach, 
intestines, and various glandular organs. 

nth Pair. Spinal Accessory. 

Apparent Origin. By two sets of filaments:— 

1. A bulbar or medullary set, four or five in number, from the lateral or 
motor tract of the lower half of the medulla oblongata, below the origin of 
the pneumogastric. 

2. A spinal set, from six to eight in number, from the lateral portion of 
the spinal cord, between the anterior and posterior roots of the upper four or 
five cervical nerves. 

Deep Origin. The medullary portion arises in a nucleus in the lower 
half of the floor of the 4th ventricle, common to the pneumogastric and 
glosso pharyngeal nerves. The spinal portion has its origin in an elongated 
nucleus lying along the external surface of the anterior cornua of the spinal 
cord, extending down to the 5th cervical vertebra. 

Distribution. From this origin the fibres unite to form a main trunk, 
which enters the cranial cavity through the foramen magnum, where it is 
at times joined by fibres from the posterior roots of the two upper cervical 
nerves, and sends filaments to the ganglion of the root of the pneumo¬ 
gastric. After emerging from the cranial cavity through the jugular fora¬ 
men, it sends a branch to the pneumogastric, and receives others in return, 
and also from the 2d, 3d and 4th cervical nerves. It divides into two 
branches: (1) An internal or anastomotic branch, made up of filaments 
coming principally from the medulla oblongata, and is distributed to the 


114 


HUMAN PHYSIOLOGY. 


muscles of the pharynx through the pharyngeal nerves coming from the 
pneumogastric; to all the muscles of the larynx, except the crico-thyroid 
through the inferior laryngeal nerve; to the heart, by filaments which 
reach it through the pneumogostric nerve. (2) An external branch, which 
is distributed to the sterno-cleido-mastoid and trapezius muscles; these 
muscles also receiving filaments from the cervical nerves. 

Properties. At its origin it is a purely motor nerve, but in its course 
exhibits some sensibility from anastomosing fibres. 

Destruction of the medullary root , by tearing it from its attachment by 
means of forceps, impairs the action of the muscles of deglutition, and 
destroys the power of producing vocal sounds by paralysis of the laryngeal 
muscles, without, however, interfering with the respiratory movements of 
the larynx ; these being controlled by other motor nerves. The normal 
rate of movement of the heart is also impaired by destruction of the 
medullary root. 

Irritation of the external branch throws the trapezius andsterno-mastoid 
muscles into convulsive movements, though section of the nerve does not 
produce complete paralysis, as they are also supplied with motor influence 
from the cervical nerves. The sterno-mastoid and trapezius muscles per¬ 
form movements antagonistic to those of respiration, fixing the head, neck 
and upper part of the thorax, and delaying the expiratory movement during 
the acts of pushing, pulling, straining, etc., and in the production of a pro¬ 
longed vocal sound, as in singing. When the external branch alone is 
divided, in animals, they experience shortness of breath during exercise, 
from a want of coordination of the muscles of the limbs and respiration ; 
and while they can make a vocal sound, it cannot be prolonged. 

Function. Governs phonation by its influence upon the vocal move¬ 
ments of the glottis; influences the movements of deglutition, inhibits the 
action of the heart and controls certain respiratory movements associated 
with sustained or prolonged muscular efforts and phonation. 

12th Pair. Hypoglossal or Sublingual. 

Apparent Origin. By two groups of filaments from the medulla ob¬ 
longata, in the grooves between the olivary body and the anterior pyramid. 

Deep Origin. From the hypoglossal nucleus situated deeply in the 
substance of the medulla, on a level with the lowest portion of the floor of 
the 4th ventricle; some decussating filaments have been traced to a higher 
encephalic centre. 

Distribution. The trunk formed by a union of the root filament 


CEREBRO-SPINAL AXIS. 


115 


passes out of the cranial cavity through the anterior condyloid foramen, 
occasionally receiving a filament from the lateral and posterior portion of 
the medulla oblongata. After emerging from the cranium, it sends filaments 
to the sympathetic and pneumogastric; it anastomoses with the lingual 
branch of the 5th pair, and receives and sends filaments to the upper cer¬ 
vical nerves. The nerve is finally distributed to the sterno-hyoid, sterno¬ 
thyroid, omo-hyoid, thyro-hyoid, stylo-glossi, hyo-glossi, genio-hyoid, genio- 
hyo-glossi, and the intrinsic muscles of the tongue. 

Properties. A purely motor nerve at its origin, but derives sensibility 
outside the cranial cavity, from anastomosis with the cervical, pneumo¬ 
gastric and 5th nerves. 

Irritation of the nerve gives rise to convulsive movements of the tongue 
and slight evidences of sensibility. 

Division of the nerve abolishes all movements of the tongue, and inter¬ 
feres considerably with the act of deglutition. 

When the hypoglossal nerve is involved in hemiplegia, the tip of the 
tongue is directed to the paralyzed side when the tongue is protruded; 
due to the unopposed action of the genio-hyo-glossus on the sound side. 

Articulation is considerably impaired in paralysis of this nerve; great 
difficulty being experienced in the pronunciation of the consonantal 
sounds. 

Mastication is performed with difficulty, from inability to retain the food 
between the teeth until it is completely triturated. 

Function. Governs all the movements of the tongue and influences the 
functions of mastication, deglutition and articulate language. 


CEREBRO-SPINAL AXIS. 

The Cerebro-Spinal Axis consists of the spinal cord, medulla oblon¬ 
gata, pons Varolii, cerebellum and cerebrum, exclusive of the spinal and 
cranial nerves. It is contained within the cavities of the cranium and 
spinal column, and surrounded by three membranes, the dura mater, 
arachnoid and pia mater, which protect it from injury and supply it with 
blood vessels. 

The Brain and Spinal Cord are composed of both white fibres and 
collections of gray cells, and are, therefore, to be regarded as conductors of 
impressions and motor impulses, as well as generators of nerve force. 


116 


HUMAN THYSIOLOGY. 


MEMBRANES. 

The Dura Mater, the most external of the three, is a tough membrane, 
composed of white fibrous tissue, arranged in bundles, which interlace in 
every direction. In the cranial cavity it lines the inner surface of the 
bones, and is attached to the edge of the foramen magnum; sends processes 
inward, forming the falx cerebri, falx cerebelli, and tentorium cerebelli, 
supporting and protecting parts of the brain. In the spinal canal it loosely 
invests the cord, and is separated from the walls of the canal by areolar 
tissue. 

The Arachnoid, the middle membrane, is a delicate serous structure 
which envelopes the brain and cord, forming the visceral layer , and is then 
reflected to the inner surface of the dura mater, forming the parietal layer. 
Between the two layers there is a small quantity of fluid which prevents 
friction by lubricating the two surfaces. 

The Pia Mater, the most internal of the three, composed of areolar 
tissue and blood vessels, covers the entire surface of the brain and cord, to 
which it is closely adherent, dipping down between the convolutions and 
fissures. It is exceedingly vascular, sending small blood vessels some dis¬ 
tance into the brain and cord. 

The Cerebro-spinal Fluid occupies the sub-arachnoid space , and the 
general ventricular cavities of the brain, which communicate by an opening, 
the foramen of Magendie, in the pia mater, at the lower portion of the 4th 
ventricle. This fluid is clear, transparent, alkaline, possesses a salt taste and 
a low specific gravity; it is composed largely of water, traces of albumen, 
glucose and mineral salts. It is secreted by the pia mater; the quantity is 
estimated from two to four fluid ozs. 

The function of the cerebro-spinal fluid is to protect the brain and cord, 
by preventing concussion from without; by being easily displaced into the 
spinal canal, prevents undue pressure and insufficiency of blood to the 
brain. 


SPINAL CORD. 

The Spinal Cord varies from 16 to 18 inches in length; is half an inch 
in thickness, weighs \ l / 2 oz., and extends from the atlas to the 2d lumbar 
vertebra, terminating in the filum terminate. It is cylindrical in shape, 
and presents an enlargement in the lower cervical and lower dorsal regions, 
corresponding to the origin of the nerves which are distributed to the 
upper and lower extremities. The cord is divided into two lateral halves 


SPINAL CORD. 


117 


by the anterior and posterior fissures. It is composed of both white or 
fibrous and gray or vesicular matter, the former occupying the exterior of 
the cord, the latter the interior, where it is arranged in the form of two 
crescents, one in each lateral half, united together by the central mass, the 
gray commissure; the white matter being united in front by the white 
commissure. 

Structure of the White Matter. The white matter surrounding each 
lateral half of the cord is made up of nerve fibres, some of which are con¬ 
tinuations of the nerves which enter the cord, while others are derived 
from different sources. It is subdivided into: (i) An Anterior column, 
comprising that portion between the anterior roots and the anterior fissure, 
which is again subdivided into two parts : (a) an inner portion, bordering 
the anterior median fissure, the direct pyramidal tract , or column of Ttirck, 
containing motor fibres which do not decussate, and which extends as far 
down as the middle of the dorsal region ; ifi) an ottter portion, surrounding 
the anterior cornua, known as the anterior root zone , composed of short 
longitudinal fibres which serve to connect together different segments of 
the spinal cord. (2) A Lateral 
column, the portion between 
the anterior and posterior roots, 
which is divisible into (a) the 
crossed pyramidal tract , occupy¬ 
ing the posterior portion of the 
lateral column, and containing 
all those fibres of the motor tract 
which have decussated at the 
medulla oblongata; it is com¬ 
posed of longitudinally running 
fibres which are connected with 
the multipolar nerve cells of the 
anterior cornua; (b) the direct 
cerebellar tract , situated upon 
the surface of the lateral column, 
consisting of longitudinal fibres 
which terminate in the cere¬ 
bellum ; it first appears in the 
lumbar region, and increases as 
it passes upward ; (r) the anterior tract, lying just posterior to the anterior 
cornua. (3) A Posterior column, the portion included between the posterior 
roots and the posterior fissure, also divisible into two portions, ( a ) an inner 


Fig.11. 


a b 



SCHEME OF THE CONDUCTING PATHS IN THE 
SPINAL CORD AT THE 3D DORSAL NERVE. 

The black part is the gray matter, v, anterior, 
hw, posterior, root; a, direct, and g, crossed, 
pyramidal tracts ; b, anterior column, ground 
bundle ; c, Goll's column ; d, postero-exter- 
nal column ; e and f, mixed lateral paths; h, 
direct cerebellar tracts.— Landois. 






118 


HUMAN PHYSIOLOGY. 


portion, the postero-internal column , or the column of Goll, bordering the 
posterior median fissure, and (b) an external portion, the postero-external 
column , the column of Burdach, lying just behind the posterior roots. 
They are composed of long and short commissural fibres which connect 
together different segments of the spinal cord. 

Structure of the Gray Matter. The gray matter, arranged in the 
form of two crescents, presents an anterior and posterior horn. It is made 
up of a delicate network of fine nerve fibres (axis cylinders), supported by 
a connective tissue framework of nucleated nerve cells, which in the anterior 
horns are large and multipolar, and connected with the anterior roots of 
spinal nerves; in the posterior horns the nerve cells are smaller, and situated 
along the inner margin, and in the caput cornu. Small cells are also found 
in the posterior vesicular columns, and in the intermediary lateral tract. 


SPINAL NERVES. 

Origin. The spinal nerves are thirty-one in number on each side of the 
spinal cord, and arise by two roots, an anterior and posterior , from the 
anterior and posterior aspects of the cord respectively: the posterior roots 
present near their emergence from the cord a small ganglionic enlargement; 
outside of the spinal canal the two roots unite to form a main trunk, which 
is ultimately distributed to the skin, muscles and viscera. 

The Function of the Anterior Roots is to transmit 7 notor impulses 
from the centres outward to the periphery. Irritation of these roots, from 
whatever cause, excites convulsive movements in the muscles to which they 
are distributed; disease or division of these roots induces a condition of 
paresis or paralysis. 

The Function of the Posterior Roots is to transmit the impressions 
made upon the periphery to the centres in the spinal cord, where they 
excite motor impulses; or to the brain, in which they are translated into 
conscious sensations. Irritation of these roots gives rise to painful sensa¬ 
tions ; division of the roots abolishes all sensation in the parts to which 
they are distributed. 

The ganglion on the posterior root influences the nutrition of the sensory 
nerve; for if the nerve be separated from the ganglion, it undergoes 
degeneration in the course of a few days, in the direction in which it 
carries impressions, i. e., from the periphery to the centres; if the nerve be 
divided between the ganglion and the cord, the central end only undergoes 


SPINAL NERVES. 


119 


degeneration. The nutrition of the anterior root is governed by nerve cells 
in the gray matter of the *cord; for if these cells undergo atrophy, or if the 
nerve be divided , it undergoes degeneration outward. 

COURSE OF THE ANTERIOR AND POSTERIOR ROOTS. 

The Anterior Roots pass through the anterior columns, horizontally, 
in straight and distinct bundles, and enter the anterior cornuse, where they 
diverge in four directions, (i) Many become connected with the prolon¬ 
gations of the multipolar nerve cells. (2) Others leave the gray matter, 
pass through the anterior white commissure, and enter the anterior columns 
of the opposite side. (3) A considerable number enter the lateral columns 
of the same side, through which they pass to the medulla oblongata, where 
they decussate and finally terminate in the corpus striatum of the opposite 
side. (4) Others traverse the gray matter horizontally, and come into 
relation with the posterior roots. 

The Posterior Roots enter the posterior horns of the gray matter (1) 
through the substantia gelatinosa, (2) through the posterior columns; of 
the former , some bend upward and downward, and become connected 
with the anterior cornuse; others pass through the posterior commissure to 
the opposite side; of the latter , fibres pass into the gray matter, to the 
posterior vesicular columns, passing obliquely through the posterior white 
columns upward and downward for some distance, and enter the gray 
matter at different heights. 

Decussation of Motor and Sensory Fibres. The Motor fibres, 
which conduct volitional impulses from the brain outward to the anterior 
cornuse, arise in the motor centres of the cerebrum; they then pass down¬ 
ward through the corona radiata, the internal capsule, the inferior portions 
of the crura cerebri, the pons Varolii, to the medulla oblongata, where the 
motor tract of each side divides into two portions, viz: 1. The larger , 
containing 91 to 97 per cent, of the fibres, which decussates at the lower 
border of the medulla and passes down in the lateral column of the oppo¬ 
site side, and constitutes the crossed pyramidal tract. 2. The smaller , 
containing 3 to 9 per cent, of the fibres, does not decussate, but passes down 
the antei'ior column of the same side, and constitutes the direct pyramidal 
tract , or the column of Tiirck. Some of the motor fibres of these two 
tracts, after entering the anterior cornuse of the gray matter, become con¬ 
nected with the large multipolar nerve cells, while others pass directly into 
the anterior roots. Through this decussation each half of the brain governs 
the muscular movements of the opposite side of the body. 


120 


HUMAN PHYSIOLOGY. 


Fig. 12. 



DIAGRAM SHOWING THE COURSE, THROUGH THE SPINAL CORD, OF THE MOTOR AND 

SENSORY NERVE FIBRES. 

B and B' represent the right and left hemispheres of the brain, from which the motor 
fibres take their origin, and in which the sensory fibres terminate. The motor tract 
from the right side 1 passes down through the crus, through the pons to the medulla 
oblongata, where it divides into two portions : ist, the larger portion , ninety-seven 
per cent., crosses over to the opposite side of the cord and passes down through the 
lateral column. It gives off fibres at different levels, which pass into the gray matter 
and become connected with the muscles, M, through the multipolar cells; the smaller 
portion , three per cent., does not cross over, but descends on the same side of the 
cord in the anterior column and supplies the muscles, ni . The same is true for the 
motor tract for the left hemisphere. 

The sensory fibres from the left side of the body enter the gray matter through the 
posterior roots. They then cross over at once to the opposite side of the cord and 
ascend to the hemisphere partly in the gray matter, partly in the posterior column. 
The same is true for the sensory nerves of the right side of the body. 
























































PROPERTIES OF THE SPINAL CORD. 


121 


The Sensory fibres, which convey the impression made upon the peri¬ 
phery to the cord and brain, pass into the cord through the posterior roots 
of spinal nerves; they then diverge and enter the gray matter at different 
levels, and at once decussate, passing to the opposite side of the gray 
matter. The sensory tract passes upward, through the cord, the medulla, 
pons Varolii, the superior portion of the crura cerebri, the posterior third 
of the internal capsule, to the sensory perceptive centre, located in the 
hippocampus major and unciate convolution (Ferrier). Through this decus¬ 
sation each half of the brain governs the sensibility of the opposite half 
of the body. 

Properties of the Spinal Cord. Irritation applied directly to the 
antero-lateral white columns produces muscular movements but no pain ; 
they are, therefore, excitable but insensible. 

The surface of the posterior columns is very sensitive to direct irritation, 
especially near the origin of the posterior roots ; less so toward the posterior 
median fissure. The sensibility is due, however, not to its own proper 
fibres, but to the fibres of the posterior root which traverse it. 

Division of the antero-lateral columns abolishes all power of voluntary 
movement in the lower extremities. 

Division of the posterior columns impairs the power of muscular coordi¬ 
nation, such as is witnessed in locomotor ataxia. 

The gray matter is probably both insensible and inexcitable under the 
influence of direct stimulation. 

A transverse section of one lateral half of the cord produces :— 

(1) On the same side, paralysis of voluntary motion and a relative or 
absolute elevation of temperature and an increased flow of blood in the 
paralyzed parts; hyperesthesia for the sense of contact, tickling, pain and 
temperature. 

(2) On the opposite side, complete anesthesia as ^regards contact, and 
tickling and temperature, in the parts corresponding to those which are 
paralyzed in the opposite side. Complete preservation of voluntary power 
and of the muscular sense. 

A vertical section through the middle of the gray matter results in the 
loss of sensation on both sides of the body below the section, but no loss of 
voluntary power. 


I 


122 


HUMAN PHYSIOLOGY. 


FUNCTIONS OF THE SPINAL CORD, 

1. As a Conductor. The Lateral columns, particularly the posterior 
portions, the “ pyramidal tracts,” and the columns of Tiirck, are the chan¬ 
nels through which pass the voluntary motor impulses from the brain to the 
large multipolar nerve cells in the anterior cornuse of gray matter, and 
through them become connected with the anterior roots which transmit the 
motor stimuli to the muscles. 

The Anterior columns , especially the portion surrounding the anterior 
cornuae, the “ anterior radicular zones,” are composed of short longitudinal 
commissural fibres, which serve to connect together different, segments of 
the spinal cord, a condition required for the coSrdination of muscular 
movements. 

The Posterior columns are composed of short and long commissural 
fibres which connect together different segments of the cord. They are 
insensible to direct irritation, but aid in the coSrdination of muscular move¬ 
ments in walking, standing, running, etc. Degeneration of the posterior 
columns gives rise to the lack of muscular coordination observed in loco¬ 
motor ataxia. 

The Gray matter , and especially that portion immediately surrounding 
the central canal, transmits the sensory nerve fibres from the posterior roots 
up to the brain. Decussation of the sensory fibres takes place throughout 
the whole length of the gray matter. 

The Multipolar cells of the anterior cornucz are connected with the 
generation and transmission of motor impulses outward; are centres for 
reflex movements; are the trophic centres for the motor nerves and muscu¬ 
lar fibres to which they are distributed. The anterior roots give passage 
to the vaso-constrictor and vaso dilator fibres which exert an influence 
upon the calibre of the blood vessels. Complete destruction of the anterior 
horns is followed by a paralysis of motion, degeneration of the anterior 
roots, atrophy of muscles and bones, and an abolition of reflex move¬ 
ments. 

2. As an Independent Nerve Centre. 

The spinal cord, by virtue of its containing ganglionic nerve matter, is 
capable of transforming impressions made upon the centripetal nerves into 
motor impulses, which are reflected outward through centrifugal nerves to 
muscles, producing movements. These reflex movements taking place 
through the gray matter, are independent of sensation and volition. 

The mechanism involved in every reflex act is a sentient surface, a sensory 
nerve, a nerve centre, a motor nerve and muscle. 


FUNCTIONS OF THE SPINAL CORD. 


123 


The reflex excitability of the cord may be— 

1. Increased by disease of the lateral columns, the administration of 
strychnia, and in frogs, by a separation of the cord from the brain, the latter 
apparently exerting an inhibitory influence over the former and depressing 
its reflex activity. 

2. Inhibited by destructive lesions of the cord, e.g., locomotor ataxia, 
atrophy of the anterior cornuse, the administration of various drugs, and, in 
the frog, by irritation of certain regions of the brain. When the cerebrum 
alone is removed and the optic lobes stimulated, the time elapsing between 
the application of an irritant to a sensory surface and the resulting movement 
will be considerably prolonged. The optic lobes (Setchenow’s centre) 
apparently generating impulses which, descending the cord, retard its reflex 
movements. 

All movements taking place through the nervous system, are of this reflex 
character, and may be divided into excito-motor, sensori-motor, and ideo¬ 
motor. 

Classification of Reflex Movements. (Kiiss ) They may be divided 
into four groups, according to the route through which the centripetal and 
centrifugal impulses pass. 

1. Those normal reflex acts, e.g., deglutition, coughing, sneezing, walk¬ 
ing, etc., pathological reflex acts, e. g., tetanus, vomiting, epilepsy, which 
take place both centripetally and centrifugally, through spinal nerves. 

2. Reflex acts which take place in a centripetal direction through a 
cerebro spinal sensory nerve, and in a centrifugal direction through a sym¬ 
pathetic motor nerve, usually a vasomotor nerve, e.g., the normal reflex 
acts, which give rise to most of the secretions, pallor and blushing of the 
skin, certain movements of the iris, certain modifications in the beat of the 
heart; the pathological, which, on account of the difficulty in explaining 
their production, are termed metastatic, e.g., ophthalmia, coryza, orchitis, 
which depend on a reflex hyperaemia; amaurosis, paralysis, paraplegia, etc., 
due to a reflex anaemia. 

3. Reflex movements, in which the centripetal impulse passes through a 
sympathetic nerve, and the centrifugal through a cerebro-spinal nerve; 
most of these phenomena are pathological, e. g., convulsions from 
intestinal irritation produced by the presence of worms, eclampsia, hysteria, 
etc. 

4. Reflex actions, in which both the centripetal and centrifugal impulses 
pass through filaments of the sympathetic nervous system, e.g., those 
obscure reflex actions which preside over the secretions of the intestinal 
fluids, which unite the phenomena of the generative organs, the dilatation 


124 


HUMAN PHYSIOLOGY. 


of the pupils from intestinal irritation (worms), and many pathological 
phenomena. 

Laws of Reflex Action. (Pfliiger.) 

1. Law of Unilaterality. If a feeble irritation be applied to one or 
more sensory nerves, movement takes place usually on one side only, and 
that upon the same side as the irritation. 

2 . Lazv of Symmetry. If the irritation becomes sufficiently intense, motor 
reaction is manifested, in addition, in corresponding muscles of the opposite 
side of the body. 

3. Law of Intensity. Reflex movements are usually more intense on the 
side of the irritation; at times the movements of the opposite side equal 
them in intensity, but they are usually less pronounced. 

4. Law of Radiation. If the excitation still continues to increase, it 
is propagated upward, and motor reaction takes place through centrifugal 
nerves coming from segments of the cord higher up. 

5. Law of Generalization. When the irritation becomes very intense, it 
is propagated to the medulla oblongata ; motor reaction then becomes gen¬ 
eral, and it is propagated up and down the cord, so that all the muscles of 
the body are thrown into action, the medulla oblongata acting as a focus 
whence radiate all reflex movements. 

Special Reflex Movements. 

There are a number of reflex movements taking place through the spinal 
cord, a study of which enables the physician to determine the condition of 
its different segments. They may be divided into, 1. Skin or superficial, 
and 2. Tendon or deep reflexes. The skin reflexes are induced by irritation 
of the skin and mucous membranes, e.g.> pricking, pinching, scratching, etc. 
The following are the principal skin reflexes :— 

1. Plantar reflex , consisting of contraction of the muscles of the foot, 
induced by stimulation of the sole of the foot; it involves the integrity of 
the reflex arc through the lower end of the cord. 

2. Gluteal reflex , consisting of contraction of the glutei muscles when 
the skin over the buttock is stimulated; it takes place through the segments 
giving origin to the fourth and fifth lumbar nerves. 

3. Cremasteric reflex , consisting of a contraction of the cremaster muscle, 
and a retraction of the testicle toward the abdominal ring, when the skin on 
the inner side of the thigh is stimulated; it depends upon the integrity of 
the segments giving origin to the first and second lumbar nerves. 

4. Abdominal reflex , consisting of a contraction of the abdominal mus¬ 
cles when the skin upon the side of the abdomen is gently scratched; its 


FUNCTIONS OF THE SPINAL CORD. 


125 


production requires the integrity of the spinal segments from the eighth to 
the twelfth. 

5. Epigastric reflex , consisting of a slight muscular contraction in the 
neighborhood of the epigastrium when the skin between the fourth and sixth 
ribs is stimulated; it requires the integrity of the cord between the fourth 
and seventh dorsal nerves. 

6. Scapular reflex consists of a contraction of the scapular muscles 
when the skin between the scapula is stimulated; it depends upon the 
integrity of the cord between the fifth cervical and third dorsal nerves. 

The superficial reflexes, though variable, are generally present in health. 
They are increased or exaggerated when the gray matter of the cord is 
abnormally excited, as in tetanus, strychnia poisoning, and in disease of 
the lateral columns, leading to arrest of their normal functions. The Ten¬ 
don or deep reflexes are also of great value in diagnosing the condition of 
the spinal segments. They are induced by a sharp blow upon a tendon. 
The following are the principal forms:— 

1. Patella reflex or Knee jerk , consisting of a contraction of the extensor 
muscles of the thigh when the ligamentum patella is struck between the 
patella and tibia. This reflex is best observed when the legs are freely 
hanging over the edge of a table. The patella reflex is generally present in 
health, being absent in only 2 per cent.; it is greatly exaggerated in lateral 
sclerosis, in descending degeneration of the cord; it is absent in locomotor 
ataxia and in atrophic lesions of the anterior gray comuse. 

2. Ankle jerk or reflex. If the extensor muscles of the leg be placed 
upon the stretch and the tendo-achillis be sharply struck, a quick extension 
of the foot will take place. 

3. Ankle clonus. This consists of a series of rhythmical reflex con¬ 
tractions of the gastrocnemius muscle, varying in frequency from 6 to 10 
per second. To elicit this reflex, pressure is made upon the sole so as to 
suddenly and energetically flex the foot at the ankle, thus putting the tendo- 
achillis upon the stretch. The rhythmical movements thus produced con¬ 
tinue so long as the tension is maintained. Ankle clonus is never present 
in health, but is very marked in lateral sclerosis of the cord. 

The toe reflex , peroneal reflex , wrist reflex are also present in sclerosis of 
the lateral columns and in the late rigidity of hemiplegia. 

Special Nerve Centres in Spinal Cord. Throughout the spinal cord 
there are a number of special nervfc centres, capable of being excited 
reflexly and producing complex coordinated movements. Though for the 
most part independent in action they are subject to the controlling influences 
of the medulla and brain. 


126 


HUMAN PHYSIOLOGY. 


1. Cilio-spinal centre, situated in the cord between the lower cervical 
and third dorsal vertebra. It is connected with the dilatation of the pupil 
through fibres which emerge in this region and enter the cervical sympa¬ 
thetic. Stimulation of the cord in this locality causes dilatation of the pupil 
on the same side; destruction of the cord is followed by contraction of the 
pupil. 

2. Genito-spinal centre, situated in the lower part of the cord. This is 
a complex centre and comprises a series of subordinate centres for the con¬ 
trol of the muscular movements involved in the acts of defecation, micturi¬ 
tion, ejaculation of semen, the movements of the uterus during parturition, 
etc. 

3. Vasomotor centres, giving origin to both vaso-constrictor and vaso¬ 

dilator fibres, which are distributed throughout the cord. Though acting 
reflexly they are under the dominating influence of the centre in the me¬ 
dulla. ' 

4. Sweat centres are also present in various parts of the cord. 

Paralysis from Injuries of the Spinal Cord. 

Seat of Lesion. If it be in the lower part of the sacral canal , there is 
paralysis of the compressor urethrae, accelerator urinae, and sphincter ani 
muscles; no paralysis of the muscles of the leg. 

At the upper limit of the sacral region. Paralysis of the muscles of 
the bladder, rectum and anus; loss of sensation and motion in the muscles 
of the legs, except those supplied by the anterior crural and obturator, 
viz.: psoas iliacus, Sartorius, pectineus, adductor longus, magnus and 
brevis, obturator, vastus externus and internus, etc. 

At the upper limit of the lumbar region. Sensation and motion para¬ 
lyzed in both legs; loss of power over the rectum and bladder; paralysis 
of the muscular walls of the abdomen interfering with expiratory move¬ 
ments. 

At the lower portion of the cervical region. Paralysis of the legs, etc. 
as above; in addition, paralysis of all the intercostal muscles and conse¬ 
quent interference with respiratory movements; paralysis of muscles of 
the upper extremities, except those of the shoulders. 

Above the middle of the cervical region. In addition to the preceding, 
difficulty of deglutition and vocalization, contraction of the pupils, paralysis 
of the diaphragm, scalene muscles, intercostals, and many of the accessory 
respiratory muscles; death resulting immediately, from arrest of respiratory 
movements. 


MEDULLA OBLONGATA. 


127 


MEDULLA OBLONGATA. 

The Medulla Oblongata is the expanded portion of the upper part of 
the spinal cord. It is pyramidal in form and measures one and a half 
inches in length, three-quarters of an inch in breadth, half an inch in 
thickness, and is divided into two lateral halves by the anterior and pos¬ 
terior median fissures, which are continuous with those of the cord. Each 


Fig. 13. 



VIEW OF CEREBELLUM IN SECTION, AND OF FOURTH VENTRICLE, WITH THE 

neighboring parts. (From Sappey ) 

1. Median groove fourth ventricle, ending below in the calamus scriptorius, with the 
longitudinal eminences formed by the fasciculi teretes, one on each side. 2. The same 
groove, at the place where the white streaks of the auditory nerve emerge from it to 
cross the floor of the ventricle. 3. Inferior peduncle of the cerebellum, formed by the 
restiform body. 4 Posterior pyramid : above this is the calamus scriptorius. 5. Supe¬ 
rior peduncle of cerebellum, or processus e cerebello ad testes. 6 6. Fillet to the side 
of the crura cerebri. 7 7. Lateral grooves of the crura cerebri. 8. Corpora quad- 
rigemina.—After Hirschfeld and Leveille. 

half is again subdivided by minor grooves, into four columns, viz.: anterior 
pyramid , lateral tract and olivary body , restiform body and posterior 
pyramid. 

1. The anterior pyramid is composed partly of fibres continuous with 
those of the anterior column of the spinal cord; but mainly of fibres de¬ 
rived from the lateral tract of the opposite side, by decussation. The 





128 


HUMAN PHYSIOLOGY. 


united fibres then pass upward through the pons Varolii and crura cerebri, 
and for the most part terminate in the corpus striatum and cerebrum. 

2. The lateral tract is continuous with the lateral columns of the cord; 
its fibres in passing upward take three directions, viz.; an external bundle 
joins the restiform body, and passes into the cerebellum; an internal bundle 
decussates at the median line and joins the opposite anterior pyramid ; a 
middle bundle ascends beneath the olivary body, behind the pons, to the 
cerebrum, as the fasciculus teres. 

The olivary body of each side is an oval mass, situated between the 
anterior pyramid and restiform body; it is composed of white matter exter¬ 
nally and gray matter internally, forming the corpus dentatutn. 

3. The restiform body , continuous with the posterior column of the cord, 
also receives fibres from the lateral column. As the restiform bodies pass 
upward they diverge and form a space, the 4th ventricle, the floor of 
which is formed by gray matter, and then turn backward and enter the 
cerebellum. 

4. The posterior pyramid is a narrow, white cord bordering the posterior 
median fissure; it is continued upward, in connection with the fasciculus 
teres, to the cerebrum. 

The Gray Matter of the medulla is continuous with that of the cord. 
It is arranged with much less regularity, becoming blended with the white 
matter of the different columns, with the exception of the anterior. By the 
separation of the posterior columns, the transverse commissure is exposed, 
forming part of the floor of the 4th ventricle; special collections of gray 
matter are found in the posterior portions of the medulla, connected with 
the roots of origin of different cranial nerves. 

Properties and Functions. The medulla is excitable anteriorly, and 
sensitive posteriorly to direct irritation. It serves (i) as a conductor of sen¬ 
sitive impressions upward from the cord, through the gray matter to the 
cerebrum ; (2) as a conductor of voluntary impulses from the brain to the 
spinal cord and ^nerves, through its anterior pyramids; (3) as a conductor 
of coordinating impulses from the cerebellum, through the restiform bodies 
to the spinal cord. 

As an Independent Reflex Centre. The medulla oblongata con¬ 
tains special collections of gray matter, which constitute independent 
nerve centres which preside over different functions, some of which are as 
follows, viz. :— 

1. A centre which controls the movements of mastication , through 
afferent and efferent nerves. (See page 25.) 


MEDULLA OBLONGATA. 129 

2. A centre reflecting impressions which influence the secretion <Jf saliva. 
(See page 28.) 

3. A centre for sucking, mastication and deglutition , whence are derived 
motor stimuli exciting to action and coordinating the muscles of the palate, 
pharynx and oesophagus, necessary for the swallowing, of the food. The 
secretion of saliva is also controlled by a centre in the medulla. 


NERVOUS CIRCLE OF DEGLUTITION. (2d and 3 d Stages.) 


Excitor 

or 

Centripetal 

Nerves. 


Palatal branch of 5th pair. 

Pharyngeal branches of the glosso pharyngeal. 
Superior laryngeal branches of the pneumogastric. 
(Esophageal branches of the pneumogastric. 


Motor 

or 

Centrifugal 

Nerves. 


Pharyngeal branches of the pneumogastric, derived 
from the spinal accessory. 

Hypoglossal and branches of the cervical plexus. 
Inferior or recurrent laryngeal. 

Motor filaments of the 3d division of the 5th pair. 
Portio dura. 


4. A centre which coordinates the muscles concerned in the act ot 
vomiting. 

5. A Speech centre , coordinating the various muscles necessary for the 
accomplishment of articulation through the hypoglossal, facial nerves and 
the 2d division of the 5th pair. 

6. A centre for the harmonization of muscles concerned in expression , 
reflecting its impulses through the facial nerve. 

7. A Cardiac centre , which exerts (1) an accelerating influence over the 
heart’s pulsations through accelerating nerve fibres emerging from the cer¬ 
vical portion of the cord, entering the inferior cervical ganglion, and thence 
passing to the heart; (2) an inhibitory or retarding influence upon the action 
of the heart, through fibres of the spinal accessory nerve running in the 
trunk of the pneumogastric. The cardio-inhibitory centre is in a state of 
tonic excitement and continuously sending impulses to the heart which 
exert an inhibitory influence upon its action. It may be stimulated directly 
by anaemia as well as venous hyperaemiaof the blood vessels of the medulla 
and increased venosity of the blood. It is excited reflexly by the stimula¬ 
tion of the central end of the vagus, sciatic and splanchnic nerves. 

8. A Vasomotor centre , which by alternately contracting and dilating 
the blood vessels through nerves distributed in their walls, regulates the 
quantity of blood distributed to an organ or tissue, and thus influences 
nutrition, secretion and calorification. The vasomotor centre is situated in 
the medulla oblongata and pons Varolii, between the corpora quadrigemina 




130 


HUMAN PHYSIOLOGY. 


and the talamus scriptorius. The vasomotor fibres having their origin in 
this centre descend through the interior of the cord, emerge through the 
anterior roots of spinal nerves, enter the ganglia of the sympathetic, and 
thence pass to the walls of the blood vessels, and maintain the arterial 
tonus ; they may be divided into two classes, viz.; vaso-dilators, e.g., 
chorda tympani, and vaso-constrictors, e.g., sympathetic fibres. 

Division of the cord at the lower border of the medulla is followed by a 
dilatation of the entire vascular system and a marked fall of the blood pres¬ 
sure. Galvanic stimulation of the divided surface of the cord is followed 
by a contraction of the blood vessels and a rise in the blood pressure. 

The vasomotor centre is stimulated directly by the condition of the 
blood in the medulla oblongata. When it is highly venous it becomes very 
active and the blood vessels throughout the body are contracted and the 
blood current becomes swifter; sudden anaemia of the medulla has a similar 
effect. This centre may be increased in action with attendant rise of 
blood pressure, by irritation of certain afferent nerve fibres. These are 
known as pressor fibres. On the other hand, its action may be depressed 
by other afferent fibres with attendant fall of blood pressure. These are 
known as depressor fibres. 

9. A Diabetic centre, irritation of which causes an increase in the amount 
of urine secreted, and the appearance of a considerable quantity of sugar. 

10. Respiratory centre , situated near the origin of the pneumogastric 
nerves, presides over the movements of respiration and its modifications, 
laughing, sighing, sobbing, sneezing, etc. It may be excited rejlexly by 
the presence of carbonic acid in the lungs irritating the terminal pneumo¬ 
gastric filaments; or automatically, according to the character of the blood 
circulating through it; an excess of carbonic acid or a diminution of oxygen 
increasing the number of respiratory movements; a reverse condition dimin¬ 
ishing the respiratory movements. 

11. A Spasm centre, stimulation of which gives rise to convulsive phe¬ 
nomena, such as coughing, sneezing, etc. 

12. A centre for certain octilar functions, governing the closure of the 
eyelids and dilatation of the pupil. 

13. A Sweat centre is also localized in the medulla. 

NERVOUS CIRCLE OF RESPIRATION (ENTIRELY REFLEX). 


Excitor 

or 

Centripetal 

Nerves. 


Pulmonary branches of the pneumogastric. 
Superior laryngeal. 

Trifacial, or 5th pair. 

Nerves of general sensibility. 

Sympathetic nerve. 



CRURA CEREBRI. 


131 


Phrenic, distributed to the diaphragm. 

Intercostals, distributed to the intercostal muscles. 
Facial nerve, or portio dura, to the facial muscles. 
External branch of spinal accessory, to the trapezius 
and sterno-cleido-mastoid muscles. 

PONS VAROLII. 

The Pons Varolii unites together the cerebrum above, the cerebellum 
behindj and the medulla oblongata below. It consists of transverse and 
longitudinal fibres, amidst which are irregularly scattered collections of gray 
or vesicular nervous matter. 

The transverse fibres unite the two lateral halves of the cerebellum. 

The longitudinal fibres are' continuous (i) with the anterior pyramids 
of the medulla oblongata, which interlacing with the deep layers of the 
transverse fibres, ascend to the crura cerebri, forming their superficial or 
fasciculated portions; (2) with fibres derived from the olivary fasciculus, 
some of which pass to the tubercula quadrigemina, while others, uniting 
with fibres from the lateral and posterior columns of the medulla, ascend 
in the deep or posterior portions of the crura cerebri. 

Properties and Functions. The superficial portion is insensible and 
inexcitable to direct irritation; the deeper portion appear to be excitable , 
consisting of descending motor fibres; the posterior portions are sensible but 
inexcitable to irritation. 

Transmits motor impulses and sensory impressions from and to the 
cerebrum. 

The gray ganglionic matter consists of centres which convert impressions 
into conscious sensations, and originate motor impulses, these taking place 
independent of any intellectual process; they are the seat of instinctive 
reflex acts; the centres which assist in the coordination of the automatic 
movements of station and progression. 


Motor 

or 

Centrifugal 

Nerves. 


CRURA CEREBRI. 

The Crura Cerebri are largely composed of the longitudinal fibres of 
the pons (anterior pyramids, fasciculi teretes); after emerging from the pons 
they increase in size, and become separated into two portions by a layer of 
dark gray matter, the locus niger. 

The stiperficial portion, the crusta, composed of the anterior pyramids, 
constitute the motor tract , which terminates, for the most part, in the corpus 



132 


HUMAN PHYSIOLOGY. 


striatum , but to some extent, also, in the cerebrum ; the deep portion , 
made up of the fasciculi teretes and posterior pyramids and accessory fibres 
from the cerebellum, constitute the sensory tract (the tegmentum), which 
terminates in the optic thalamus and cerebrum. 

Function. The crura are conductors of motor impulses and sensory 
impressions; the gray matter, the locus niger , assists in the coordination of 
the complicated movements of the eyeball and iris, through the motor oculi 
communis nerve. They also assist in the harmonization of general muscular 
movements; section of one crus giving rise to peculiar movements of rotation 
and somersaults forward and backward. 


CORPORA QUADRIGEMINA. 

The Corpora Quadrigemina are four small, rounded eminences, two 
on each side of the median line, situated immediately behind the third 
ventricle, and beneath the posterior border of the corpus callosum. 

The anterior tubercles are oblong from before backward, and larger than 
the posterior , which are hemispherical in shape; they are grayish in color, 
but consist of white matter externally and gray matter internally. 

Both the anterior and posterior tubercles are connected with the optic 
thalami by commissural bands named the anterior and posterior brachia , 
respectively. They receive fibres from the olivary fasciculus and fibres 
from the cerebellum, which pass upward to enter the optic thalami. 

The corpora geniculata are situated, one on the inner side and one on 
the outer side of each optic tract, behind and beneath the optic thalamus, 
and from their position are named the corpora geniculata interna and 
exte?-na; they give origin to fibres of the optic nerve. 

Functions. The Tubercula quadrigemina are the physical centres of 
sight, translating the luminous impressions into visual sensations. Destruc¬ 
tion of these tubercles is immediately followed by a loss of the sense of 
sight; moreover, their action in vision is crossed, owing to the decussation 
of the optic tracts, so that if the tubercle of the right side be destroyed by 
disease or extirpated, in a pigeon, the sight is lost in the eye of the oppo¬ 
site side, and the iris loses its mobility. 

The tubercula quadrigemina as nerve centres preside over the reflex 
movements which cause a dilation or contraction of the iris; irritation of 
the tubercles causing contraction, destruction causing dilatation. Removal 
of the tubercles on one side produces a temporary loss of power of the 
opposite side of the body, and a tendency to move around an axis is mani- 


CORPORA STRIATA AND OPTIC THALAMI. 133 

fested, as after a section of one crus cerebri, which, however, may be due 
to giddiness and loss of sight. 

They also assist in the coordination of the complex movements of the 
eye, and regulate the movements of the iris during the movements of 
accommodation for distance. 


CORPORA STRIATA AND OPTIC THALAMI. 

The Corpora Striata are two large ovoid collections of gray matter, 
situated at the base of the cerebrum, the larger portions of which are 
imbedded in the white matter, the smaller portions projecting into the 
anterior part of the lateral ventricle. Each striated body is divided, by a 
narrow band of white matter, into two portions, viz :— 

1. The Caudate nucleus , the intraventricular portion, which is conical 
in shape, having its apex directed backward, as a narrow, tail-like process. 

2 . The Lenticular nucleus , imbedded in the white matter, and for the 
most part external to the ventricle; on the outer side of the lenticular 
nucleus is found a narrow band of white matter, the external capsule; 
and between it and the convolutions of the island of Reil, a thin band of 
gray matter, the claustrum ; the corpora striata are grayish in color, and 
when divided present transverse striations, from the intermingling of white 
fibres and gray cells. 

The Optic Thalami are two oblong masses situated in the ventricles 
posterior to the corpora striata, and resting upon the posterior portion of 
the crura cerebri. The internal surface projecting into the lateral ven¬ 
tricles is white, but the interior is grayish, from a commingling of both 
white fibres and gray cells. Separating the lenticular nucleus from the 
caudate nucleus and the optic thalamus, is a band of white tissue, the 
internal capsule. 

The internal capsule is a narrow, bent tract of white matter, and is, for 
the most part, an expansion of the motor tract of the crura cerebri. It 
consists of two segments, an anterior , situated between the caudate 
nucleus and the anterior surface of the lenticular nucleus, and a posterior , 
situated between the optic thalamus and the posterior surface of the len¬ 
ticular nucleus. These two segments unite at an obtuse angle, which is 
directed toward the median line. Pathological observation has shown 
that the nerve fibres of the direct and crossed pyramidal tracts can be 
traced upward through the anterior two-thirds of the posterior segment, 
into the centrum ovale, where, for the most part, they are lost; a portion, 


134 


HUMAN PHYSIOLOGY. 


however, remaining united, ascend higher and terminate in the paracentral 
lobule, the superior extremity of the ascending frontal and parietal convo¬ 
lutions. The sensory tract can be traced upward, through the posterior 
third, into the cerebrum, where they probably terminate in the hippo¬ 
campus major and unciate convolution. 

Functions. The Corpora striata are the centres in which terminate 
some of the fibres of the superficial or motor tract of the crura cerebri; 
others pass upward through the internal capsule , to be distributed to the 
cerebrum. It might be inferred, from their anatomical relations, that they 
are motor centres. Irritation by a weak galvanic current produces mus¬ 
cular movements of the opposite side of the body; destruction of their 
substance by a hemorrhage, as in apoplexy, is followed by a paralysis of 
motion of the opposite side of the body, but there is no loss of sensation. 
When the hemorrhagic destruction involves the fibres of the anterior two- 
thirds of the posterior segment of the internal capsule, and thus separates 
them from their trophic centres in the cortical motor region, a descending 
degeneration is established, which involves the direct pyramidal tract of 
the same side and the crossed pyramidal tract of the opposite side. 

Destruction of the posterior one-third of the posterior segment of the 
internal capsule is followed by a loss of sensation on the opposite side of the 
body, and a loss of the senses of smell and vision on the same side (Charcot). 
The precise function of the corpora striata is unknown, but they are in some 
way connected with motion. 

The Optic thalami receives the fibres of the tegmentum , the posterior 
portion of the crura cerebri. They are insensible and inexcitable to direct 
irritation. Removal of one optic thalamus, or destruction of its substance 
by disease or hemorrhage, is followed by a loss of sensibility of the opposite 
side of the body, but there is no loss of motion; their precise function is 
also unknown, but in some way connected with sensation. In both cases 
their action is crossed. 


CEREBELLUM. 

The Cerebellum is situated in the inferior fossae of the occipital bone, 
beneath the posterior lobes of the cerebrum. It attains its maximum 
weight, which is about 5 ozs., between the twenty-fifth and fortieth years ; 
the proportion between the cerebellum and cerebrum being 1 to 8£. 

It is composed of two lateral hemispheres and a central elongated lobe, 
the vermiform process ; the two hemispheres are connected with each other 
by the fibres of the middle peduncle forming the superficial portion of the 


CEREBELLUM. 


135 


pons Varolii. It is brought into connection with the medulla oblongata 
and spinal cord, through the prolongation of the restiform bodies; with 
the cerebrum, by fibres passing upward beneath the corpora quadrigemina 
and the optic thalami, and then forming part of the diverging cerebral 
fibres. 

Structure. It is composed of both white and gray matter, the former 
being internal, the latter external, and convoluted, for economy of space. 

The White matter consists of a central stem, the interior of which ^s a 
dentated capsule of gray matter, the corpus dentatum. From the external 
surface of the stem of white matter processes are given off, forming the 
lamince , which are covered with gray matter. 

The Gray 7 natter is convoluted and covers externally the laminated pro¬ 
cesses; a vertical section through the gray matter reveals the following 
structures:— 

1. A delicate connective tissue layer , just beneath the pia mater, contain¬ 
ing rounded corpuscles, and branching fibres passing toward the external 
surface. 

2. The cells of Purkinje, forming a layer of large, nucleated, branched 
nerve cells sending off processes to the external layer. 

3. A granular layer of small, but numerous corpuscles. 

4. Nerve fibre layer , formed by a portion of the white matter. 

Properties and Functions. Irritation of the cerebullum is not followed 
by any evidences either of pain or convulsive movements; it is, therefore, 
insensible and inexcitable. 

Co-ordination of Movements. Removal of the superficial portions 
of the cerebellum in pigeons produces feebleness and want of harmony in 
the muscular movements; as successive slices are removed, the movements 
become more irregular, and the pigeon becomes restless; when the last 
portions are removed, all power of flying , walking , standing , etc., is entirely 
gone, and the equilibrium cannot be maintained, the power of coordinating 
muscular movements being entirely gone. The same results have been 
obtained by operating on all classes of animals. 

The following symptoms were noticed by Wagner, after removing the 
whole or a large part of the cerebellum. 1. A tendency on the part of the 
animal to throw itself on one side, and to extend the legs as far as possible. 
2. Torsion of the head on the neck. 3. Trembling of the muscles of the 
body, which was general. 4. Vomiting and* occasionally liquid evacua¬ 
tions. 

Forced Movements. Division of one crus cerebelli causes the animal 


136 


HUMAN PHYSIOLOGY. 


to fall on one side and roll rapidly on its longitudinal axis. According to 
Schiff, if the peduncle be divided from behind , the animal falls on the same 
side as the injury; if the section be made in front , the animal turns to the 
opposite side. 

Disease of the cerebellum partially corroborates the result of experi¬ 
ments ; in many cases symptoms of unsteadiness of gait, from a want of 
coordination , have been noticed. 

Comparative anatomy reveals a remarkable correspondence between the 
development of the cerebellum and the complexity of muscular actions. It 
attains a much greater development, relatively to the rest of the brain, in 
those animals whose movements are very complex and varied in character, 
such as the kangaroo, shark and swallow. 

The cerebellum may possibly exert some influence over the sexual func¬ 
tion, but physiological and pathological facts are opposed to the idea of its 
being the seat of the sexual instinct. It appears to be simply a centre for 
the coordination and equilibration of muscular movements. 


CEREBRUM. 

The Cerebrum is the largest portion of the encephalic mass, constituting 
about four-fifths of its weight; the average weight in the adult male is from 
48 to 50 ozs., or about three pounds, while in the adult female it is about 
five ozs. less. After the age of forty the weight of the cerebrum gradually 
diminishes at the rate of one ounce every ten years. In idiots the brain 
weight is often below the normal, at times not amounting to more than 
twenty ounces. 

The Blood Supply to the cerebrum is unusually large, considering its 
comparative bulk ; nearly one-fifth of the entire volume of blood being dis¬ 
tributed to it by the carotid and vertebral arteries. These vessels anastomose 
so freely, and are so arranged within the cavity of the cranium, that an 
obstruction in one vessel will not interfere with the regular supply of blood 
to the parts to which its branches are distributed. A diminished amount, or 
complete cessation, of the supply of blood is at once followed by a sus¬ 
pension of its functional activity. 

The cerebrum is connected with the pons Varolii and medulla oblongata 
through the crura cerebri, and with the cerebellum, through the superior 
peduncles. It is divided into two lateral halves, or hemispheres, by the 
longitudinal fissure running from before backward in the median line; each 
hemisphere is composed of both white and gray matter, the former being 


CEREBRUM. 


137 


internal, the latter external; it covers the surfaces of the hemisphere which 
are infolded, forming convolutions, for economy of space. 

Fissures. 

1. The Fissure of Sylvius is one of the most important; it is the first to 
appear in the development of the foetal brain, being visible at about the 
third month; in the adult it is quite deep and well marked, running from 
the under surface of the brain upward, outward and backward, and forms 
a boundary between the frontal and temporo-sphenoidal lobes. 

2. The Fissure of Rolando is second in importance, and runs from a 
point on the convexity near the median line transversely outward and down¬ 
ward toward the fissure of Sylvius, but does not enter it. It separates the 
frontal from the parietal lobe. 

3. The Parietal fissure , arising a short distance behind the fissure of 
Rolando, upon the convexity of the hemisphere, runs downward and back¬ 
ward to its posterior extremity. 

4. The Parieto-occipitalfissure separating the occipital from the parietal 
lobes. Beginning upon the outer surface of the cerebrum, it is continued 
on the mesial aspect downward and forward until it terminates in the calca¬ 
rine fissure. 

5. The Calloso-marginal fissure lying upon the mesial surface, where it 
runs parallel with the corpus callosum. 

Secondary fissures of importance are found in different lobes of the 
cerebrum, separating the various convolutions. In the anterior lobe 
are found the pre-central , superior frontal and inferior frontal fissures ; 
in the temporo-sphenoidal lobes are found the first and second iemporo- 
sphenoidalfissures ; in the occipital lobe, the calcarine and hippo-campal 
fissures. 

Convolutions. Frontal lobe. 

The Ascending frontal convolution , situated in front of the fissure of 
Rolando, runs downward and forward ; it is continuous above with the 
anterior frontal, and below with the inferior frontal convolution. 

The Superior frontal convolution is bounded internally by the longitu¬ 
dinal fissure, and externally by the superior frontal fissure; it is connected 
with the superior end of the frontal convolution, and runs downward and 
forward to the anterior extremity of the frontal lobe, where it turns back¬ 
ward, and rests upon the orbital plate of the frontal bone. 

The Middle frontal convolution , the largest of the three, runs from be¬ 
hind forward, along the sides of the lobe, to its anterior part; it is bounded 
above by the superior and below by the inferior frontal fissures. 

J 


138 


HUMAN PHYSIOLOGY. 


The Inferior frontal convolution winds around the ascending branch of 
the fissure of Sylvius, in the anterior and inferior portion of the cerebrum. 

Parietal Lobe. The Ascending parietal convolution is situated just 
behind the fissure of Rolando, running downward and forward; above, it 
becomes continuous with the upper parietal convolution, and below, winds 
around to be united with the ascending frontal. 

Fig. 14. 


r 



diagram showing fissures and convolutions of the left side of the human 

BRAIN. 

F, frontal; P, parietal; O, occipital; T, temporo-sphenoidal lobe ; S. fissure of Sylvius ; 
S', horizontal; S", ascending ramus of S ; c, sulcus centralis, or fissure of Rolando ; 
A, ascending frontal, and B, ascending parietal, convolution ; Fj, superior ; F 2 , middle, 
and F 3 , inferior frontal convolutions; fj, superior, f 2 , inferior, frontal fissures; 
f 3 , sulcus praecentralis ; P, superior parietal lobule; P 2 , inferior parietal lobule, con¬ 
sisting of P 2 , supra-marginal gyrus, and P' 2 , angular gyrus ; ip, sulcus interparietalis ; 
c m, termination of calloso-marginal fissure; Oi, first, 0 2 , second, 0 3 , third, occipital 
convolutions ; p o , parieto-occipital fissure ; o, transverse occipital fissure ; o%, inferior 
longitudinal occipital fissure; Tj, first, T 2 , second, T 3 , temporo-sphenoidal, convolu¬ 
tions, ti, first, second, temporo-sphenoidal fissures.— Landois’ Physiology. 















CEREBRUM. 


139 


The Upper parietal convolution is situated between the parietal and 
longitudinal fissures. 

The Supra-i?iarginal convolution winds around the superior extremity 
of the fissure of Sylvius. 

The Angular convolution , a continuation of the preceding, follows the 
parietal fissure to its posterior extremity, and then makes a sharp angle 
downward and forward. 

Temporo-sphenoidal Lobe. Contains three well-marked convolu¬ 
tions, the superior, middle and inferior , separated by well-defined fissures, 
and continuous posteriorly with the convolutions of the parietal lobe. 

The Occipital Lobe lies behind the parieto-occipital fissure, and con¬ 
tains the superior , middle and inferior convolutions, not well marked. 

The Central Lobe, or Island of Reil , situated at the bifurcation of the 
fissure of Sylvius, is a triangular-shaped cluster of six convolutions, the 
gyri oferti , which are connected with those of the frontal, parietal, and 
temporo-sphenoidal lobes. 

Upon the inner or mesial aspect of the hemisphere are found (Fig. 15)— 

1. The Paracentral lobule , lying in the region of the upper extremity of 
the fissure of Rolando; it contains the large giant cells of Betz. Injury to 
this convolution is followed by degeneration of the motor tract. 

2. The Gyrus fornicatus , lying below the calloso-marginal fissure. 
Running parallel with the corpus callosum, it terminates at its posterior 
border in the hippocampal gyrus. 

3. The Gyrus hippocampus (H) is formed by the union of the preceding 
convolution with the occipito-temporal. It runs forward and terminates 
in a hooked extremity— uncus. 

4. The Quadrate lobule or precuneus lies between the upper extremity 
of the calloso marginal fissure and the parieto-occipital. 

5. The Cuneus lies posteriorly to the quadrate lobule. It is a wedge- 
shaped mass enclosed by the calcarine and parieto-occipital fissures. 

Structure. The Gray matter of the cerebrum, about one-eighth of an 
inch thick, is composed of five layers of nerve cells: (1) a superficial layer, 
containing few small multipolar ganglion cells; (2) small ganglion cells, 
pyramidal in shape; (3) a layer of large pyramidal ganglion cells with 
processes running off superiorly and laterally; (4) the granular formation 
containing nerve cells; (5) spindle-shaped and branching nerve cells of 
moderate size. 

The White matter consists of three distinct sets of fibres:— 

I. The divergmg or peduncular fibres are mainly derived from the 


140 


HUMAN PHYSIOLOGY. 


columns of the cord and medulla oblongata; passing upward through the 
crura cerebri, they receive accessory fibres from the olivary fasciculus, cor¬ 
pora quadrigemina and cerebellum. Some of the fibres terminate in the 
optic* tbalami and corpora striata, while others radiate into the anterior 
middle and posterior lobes of the cerebrum. 

2. The transverse commissural fibres connect together the two hemi¬ 
spheres, through the corpus callosum and anterior and posterior commis¬ 
sures. 

3. The longitudinal comtnissural fibres connect together different parts 


of the same hemisphere. 

Fig. 15 . 



DIAGRAM SHOWING FISSURES AND CONVOLUTIONS ON MESIAL ASPECT OF THE RIGHT 


HEMISPHERE. 

Median aspect of the right hemisphere. CC, corpus callosum divided longitudinally: 
Gf, gyrus fornicatus ; H, gyrus hippocampi; h, sulcus hippocampi; U, uncinate 
gyrus ; c?n, calloso-marginal fissure ; F, first frontal convolution ; c, terminal portion 
of fissure of Rolando; A, ascending frontal; B, ascending parietal convolution and 
paracentral lobule; P/, praecuneus or quadrate lobule; Oz, cuneus; Po, parieto¬ 
occipital fissure; o\, transverse occipital fissure; oc, calcarine fissure; oc', superior, 
oc", inferior ramus of the same ; D, gyrus descendens; T4, gyrus occipito-temporalis 
lateralis (lobulus fusiformis); T 5 , gyrus occipito-temporalis medialis (lobulus lin- 
gualis). 


Functions. The cerebral hemispheres are the centres of the nervous 
system through which are manifested all the phenomena of the mind; 
they are the centres in which impressions are registered, and reproduced 
subsequently as ideas; they are the seat of intelligence, reason and will. 












Fig. 16. 


SIDE VIEW OF THE BRAIN OF MAN, WITH THE AREAS OF THE CEREBRAL CONVOLUTIONS, 

ACCORDING TO FERRIER. 

The figures are constructed by marking on the brain ofi man, in their respective 

situations, the areas ofi the brain ofi the monkey as determined by experiment , and 

the description ofi the efifiects ofi stimulating the various areas refiers to the brain of 

the monkey. 

(1) Advance of the opposite hind limb, as in walking. 

(2) , (3)> (4) Complex movements of the opposite leg and arm, and of the trunk, as in 
swimming. 

(а) , ( b ), (c), (d) Individual and combined movements of the fingers and wrist of the 
opposite hand. Prehensile movements. 

(5) Extension forward of the opposite arm and'hand. 

(б) Supination and flexion of the opposite forearm. 

(7) Retraction and elevation of the opposite angle of the mouth, by means of the zygo¬ 
matic muscles. 

(8) Elevation of the ala nasi and upper lip, with depression of the lower lip on the oppo¬ 
site side. 

(9) , (10) Opening of the mouth, with (9) protrusion and (to) retraction of the tongue; 
region of aphasia, bilateral action. 

(11) Retraction of the opposite angle of the mouth, the head turned slightly to one side. 

(12) The eyes open widely, the pupils dilate and the head and eyes turn toward the 
opposite side. 

( 1 3) , (ifi) The eyes move toward the opposite side with an upward (13) or downward 
(13O deviation. The pupils are generally contracted. 

(14) Pricking of the opposite ear, the head and eyes turn to the opposite side, and the 
pupils dilate largely. 


141 











142 


HUMAN PHYSIOLOGY. 


However important a centre the cerebrum may be, for the exhibition of 
this highest form of nervous action, it is not directly essential for the con¬ 
tinuance of life; for it does not exert any control over those automatic 
reflex acts, such as respiration, circulation, etc., which regulate the functions 
of organic life. 

From the study of comparative anatomy, pathology, vivisection, etc., 
evidence has been obtained which throws some light upon the physiology 
of the cerebral hemispheres. 

1. Comparative Anatomy shows that there is a general connection be¬ 
tween the size of the brain, its texture, the depth and number of convolu¬ 
tions, and the exhibition of mental power. Throughout the entire animal 
series, the increase in intelligence goes hand in hand with an increase in 
the development of the brain. In man there is an enormous increase in 
size over that of the highest animals, the anthropoids. The most cultivated 
races of men have the greatest cranial capacity; that of the educated 
European being about 116 cubic inches, that of the Australian being about 
60 cubic inches, a difference of 56 cubic inches. Men distinguished for 
great mental power usually have large and well-developed brains; that of 
Cuvier weighed 64 ozs.; that of Abercrombie 63 ozs.; the average being 
about 48 to 50 ozs.; not only the size, but above all, the texture of the 
brain, must be taken into consideration. 

2. Pathology. Any severe injury or disease disorganizing the hemi¬ 
spheres is at once attended by a disturbance, or entire suspension of mental 
activity. A blow on the head producing concussion, or undue pressure 
from cerebral hemorrhage destroys consciousness; physical and chemical 
alterations in the gray matter have been shown to coexist with insanity ? 
loss of memory, speech, etc. Congenital defects of organization from im¬ 
perfect development are usually accompanied by a corresponding deficiency 
of intellectual power and the higher instincts. Under these circumstances 
no great advance in mental development can be possible, and the intelli¬ 
gence remains at a low grade. In congenital idiocy not only is the brain 
of small size, but it is wanting in proper chemical composition; phosphorus , 
a characteristic ingredient of the nervous tissue, being largely diminished 
in amount. 

3. Experimentation upon the lower animals by removing the cerebral 
hemispheres is attended by results similar to those observed in disease and 
injury. Removal of the cerebrum in pigeons produces complete abolition 
of intelligence, and destroys the capability of performing spontaneous move¬ 
ments. The pigeon remains in a condition of profound stupor, which is 
not accompanied, however, by a loss of sensation, or of the power of pro- 


CEREBRAL LOCALIZATION OF FUNCTION. 


143 


ducing reflex or instinctive movements. The pigeon can be temporarily 
aroused by pinching the feet, loud noises, light placed before the eyes, etc., 
but soon relapses into a state of quietude, being unable to remember im¬ 
pressions and connect them with any train of ideas; the faculties of 
memory, reason and judgment being completely abolished. 


CEREBRAL LOCALIZATION OF FUNCTION. 

From experiments made upon animals, and the results of clinical and post¬ 
mortem observations upon men, it has been shown that the phenomena of 
organic and psychical life are presided over by anatomically localized centres 
in the brain. A knowledge of the position of these centres becomes of the 
highest importance in localizing the seat of lesions, thrombi, hemorrhages, 
new growths, etc., which show themselves in paralysis, epilepsies, etc. 
It has not been possible to thus localize all functions, and to many parts of 
the brain no special use can be assigned. The following are the centres 
most definitely mapped out and that are of paramount importance:— 

Motor Centres. These are in the cortical gray matter, and are arranged 
along either side of the fissure of Rolando. This area is known as the 
motor area or 7 notor zone , stimulation of which is followed by convulsive 
movements of the muscles of the opposite side of the body, while destruc¬ 
tion of the gray matter of this area is followed by permanent paralysis of 
the muscles of the opposite side. From experiments made upon monkeys, 
Ferrier has mapped out a number of motor centres which he has transferred 
to corresponding localities on the human brain (see Fig. 16). The descrip¬ 
tive test of the figure renders his results intelligible. Pathological studies 
have largely confirmed his deductions. In a general way it may be said 
that the upper third of the ascending frontal and parietal convolutions 
about this fissure preside over the movements of the leg of the opposite side 
of the body; the middle third controls the movements of the arm; the 
upper part of the inferior third is the facial area. The lowest part of the 
inferior third governs the motility of the lips and tongue, and this space, 
with the posterior extremity of the third frontal convolution, constitutes the 
speech centre. 

The experiments of Horsley and Schafer have enabled them to furnish 
a new diagrammatic representation of the motor area and to more accurately 
define the special areas upon the lateral and mesial aspects of the brain of 
the monkey. The boundaries of the general and special areas as deter- 


144 


HUMAN PHYSIOLOGY. 


mined by these observers will be readily understood by an examination of 
Figures 17 and 18. 

For diagnostic purposes the motor areas for the face and limbs have been 
subdivided as follows :— 

1. The face area may be divided into an upper part comprising about 
one-third, and a lower part comprising the remaining two-thirds. In the 
upper part are centres governing the movements of the muscles of the oppo¬ 
site angle of the t)iouth and of the lower face. The anterior portion of the 
lower two-thirds controls the movements of the vocal cords and may be 
regarded as a laryngeal centre; the posterior portion governs the opening 
and shutting of the mouth and the protrusion and retraction of the tongue. 

2. The upper limb area may be subdivided as follows : The upper part 


Fig. 17. 



DIAGRAM OF THE MOTOR AREAS ON THE OUTER SURFACE OF A MONKEY’S BRAIN. 

Horsley and Schafer. 

controls the movements of the shoulder; posterior and below this point are 
centres for the elbow; below and anteriorly, centres for the wrist and finger 
movements, while lowest and posteriorly centres governing the thumb. 

3. The leg area may be subdivided as follows : The anterior part, both 
on the mesial and lateral surfaces, contains centres governing the hip and 
thigh movements; in the posterior part are centres for the movements of 
the leg and toes. The centre for the big toe has been located in the para¬ 
central lobule. 

4. The trunk area , situated largely on the mesial surface, contains 
anteriorly centres governing the rotation and arching of the spine, while 
posteriorly are found centres governing movements of the tail and pelvis. 

5. The head area , or area for visual direction , contains centres, excita- 



CEREBRAL LOCALIZATION OF FUNCTION. 


145 


tion of which causes “ opening of the eyes, dilatation of the pupils and 
turning of the head to the opposite side with conjugate deviation of the 
eyes to that side.” 

The centres of origin of the nerves for the ocular muscles lie in 
the gray matter of the aqueduct of Sylvius. Destruction of the gray 
matter at these points is followed by paralysis of the muscles of the 
opposite side of the body, and morbid growths, hemorrhages or thrombi of 
the vessels of the parts, result in abnormal stimulation or interference of the 
functions corresponding to the nature and extent of the lesion. Cerebral or 
Jacksonian epilepsy is a result of local cortical disease. 

Centre for Speech. Pathological investigations have demonstrated 
that the left third frontal convolution is of essential importance for speech. 


Fig. 18. 



DIAGRAM OF THE liOTOR AREAS ON THE MARGINAL CONVOLUTION OF A MONKEY’S 
brain.— Horsley and Schafer. 

Adjoining this convolution are the centres controlling the motility of the 
lips, tongue, etc. In the majority of the cases the speech centres are on the 
left side of the brain, though in exceptional cases it is on the right side, 
especially in left-handed people. In deaf-mutes this convolution is very 
imperfectly developed, while in monkeys it is quite rudimentary. 

Lesions of the third frontal convolution on the left side, if the patient be 
right-handed, produce the various forms of aphasia or the partial or com¬ 
plete loss of the power of articulate speech. 

Aphasia is of many degrees and kinds. In alaxic aphasia the patient is 
unable to communicate his thoughts by words, there being an inability to 
execute the movements of the mouth, etc., necessary for speech. In 






146 


HUMAN PHYSIOLOGY. 



agraphic aphasia there is an inability to execute the movements necessary 
for writing, though the mental processes are retained. In the ataxic form 
the lesion is in the 3d frontal convolution, and in the agraphic form it is in 
the arm centre. 

In Amnesic Aphasia there is a loss of the memory of words, the purest 
examples of which consist of the affections known as word deafness and 
word blindness. In word deafness the patient cannot understand vocal 
speech, though he is capable of hearing other sounds. This condition is 
associated with lesion of the first temporal convolution. In word blindness 

the patient cannot name a 
FlG - j 9 - letter or a word when 

printed or written, though 
he can see all other objects. 
This condition is associated 
with impairment of the visual 
centres. 

Figure 19 will illustrate 
the conditions in the various 
forms of aphasia. Impres¬ 
sions are constantly passing 
from eye and ear to the 
visual and auditory centres 
and there registered. Com¬ 
missural fibres connect these 
centres with the arm and 
speech centres, which in turn 
are connected by efferent 
fibres with the muscles of 
the hand and vocal appa¬ 
ratus. Muscular movements 
of the eyes, hand and mouth 
are also registered by means 
of the afferent fibres s, s', s // . 

Sensory Centres. These 
are the centres in which the 
sensory impressions are co¬ 
ordinated, and in which they 
probably become parts of our consciousness. The most important are 
The Visual Centre , located in the occipital lobe and especially in the 
cuneus. Unilateral destruction of this area results in hemianopsia , or 






SYMPATHETIC NERVOUS SYSTEM. 


147 


blindness of the corresponding halves of the two retinae. Destruction of 
both occipital lobes in man results in total blindness. Stimulation or irri¬ 
tation of the visual centre causes photopsia, or hallucinations of sight, in 
corresponding halves of the retinae. There have been instances of injury of 
these parts when sensations of color were abolished with preservation of 
those of space and light, thus showing a special localization of the color 
centre. Late experiments show that the centres of the two hemispheres are 
united, as ocular fatigue of a non-used eye was proportional to the fatigue 
of the exercised one. 

The Auditory Centres are located in the temporo-sphenoidal lobes. 
Word deafness is associated with softening of these parts, and their complete 
removal results in deafness. 

The Gustatory and Olfactory Centres are located in the uncinate gyrus, 
on the inner side of the temporo-sphenoidal lobes. There does not seem to 
be any differentiation, up to this time, of these two centres. 

The centre for tactile impressions was located by Ferrier in the hippo¬ 
campal region. Horsley and Schafer found that destructive lesions of the 
gyrus fornicatus was followed by hemianaesthesia of the opposite side of the 
body, which was more or less marked and persistent. These observers 
concludethat the limbic lobe “ is largely, if not exclusively, concerned in the 
appreciation of sensations painful and tactile.” 

The Stiperior and Middle Frontal convolutions appear to be the seat of 
the reason, intelligence and will. Destruction of these parts is fol¬ 
lowed by proportional hebetude, without any impairment of sensation or 
motion. 


SYMPATHETIC NERVOUS SYSTEM. 

The Sympathetic Nervous System consists of a chain of ganglia 
connected together by longitudinal nerve filaments, situated on each side of 
the spinal column, running from above downward. The two ganglionic 
cords are connected together in the interior of the cranium by the ganglion 
of Ribes, on the anterior communicating artery, and terminate in the gan¬ 
glion impar, situated at the top of the coccyx. 

The chain of ganglia is divided into groups, and named according to the 
location in which they are found, viz.: cranial, four in number ; cervical, 
three; thoracic, twelve; lumbar, five; sacral, five; coccygeal, one. Each 
ganglion consists of a collection of vesicular nervous matter, bundles of 
non-medullated nerve fibres, imbedded in a capsule of connective tissue. 


148 


HUMAN PHYSIOLOGY. 


The ganglia are reinforced by motor and sensory fibres from the cerebro¬ 
spinal nervous system. 

The Ganglia have distinct nerve fibres from which branches are dis¬ 
tributed to the glands, arteries, muscles, and to the cerebral and spinal 
nerves; many pass, also, to the visceral ganglia, e.g., cardiac, semilunar, 
pelvic, etc. 

Cephalic Ganglia. 

1. The Ophthalmic or Ciliary ganglion is situated in the orbital cavity 
posterior to the eyeball; it is of small size, and of a reddish-gray color; 
receives filaments of communication from the motor oculi, ophthalmic branch 
of the 5th pair, and the carotid plexus. Its filaments of distribution are the 
ciliary nerves, which consist of— 

1. Motor fibres for the circular fibres of the iris and ciliary muscle. 

2. Sensory fibres for the cornea, iris and associated parts. 

3. Vasomotor fibres for the blood vessels of the choroid, iris and 
retina. 

4. Motor fibres for the dilator fibres of the iris. 

2. The Sphenopalatine , or Meckel’s ganglion, triangular in shape, is 
situated in the spheno-maxillary fossa; receives filaments from the facial 
(Vidian nerve), and the superior maxillary branch of the 5th nerve Its 
filaments of distribution pass to the gums, the soft palate, levator palati and 
azygos uvulae muscles. 

3. The Otic , or Arnold’s ganglion, is of small size, oval in shape, and 
situated beneath the foramen ovale; receives a motor filament from the 
facial and sensory filaments from the glosso-pharyngeal and 5th nerve; 
sends filaments to the mucous membrane of the tympanic cavity and to the 
tensor tympani muscle. 

4. The Submaxillary ganglion, situated in the submaxillary gland, 
receives filaments from the chorda tympani, sensory filaments from the lin¬ 
gual branch of the 5th nerve, and filaments from the sympathetic. The 
chorda tympani nerve supplies vaso-dilator and secretory fibres to the sub¬ 
maxillary and sub-lingual glands. The fifth nerve endows the glands with 
sensibility, while the sympathetic supplies secretory or trophic fibres. 

Cervical Ganglia. 

The Superior cervical ganglion is fusiform in shape, of a grayish-red 
color, and situate opposite the 2d and 3d cervical vertebrae; it sends 
branches to form the carotid and cavernous plexuses which follow the 
course of the carotid arteries to their distribution; also sends branches to 


SYMPATHETIC NERVOUS SYSTEM. 


149 


join the glosso-pharyngeal and pneumogastric, to form the pharyngeal 
plexus. 

The Middle cervical ganglion, the smallest of the three, is occasionally 
wanting; it is situated opposite the 5th cervical vertebra; sends branches 
to the superior and inferior cervical ganglion, and to the thyroid artery. 

The Inferior cervical ganglion, irregular in form, is situated opposite the 
last cervical vertebra; it is frequently fused with the first thoracic ganglion. 

The superior , middle and inferior cardiac nerves , arising from these 
cervical ganglia, pass downward and forward to form the deep and super¬ 
ficial, cardiac plexuses located at the bifurcation of the trachea, from which 
branches are distributed to the heart, coronary arteries, etc. 

The Thoracic Ganglia are usually twelve in number, placed against 
the heads of the ribs behind the pleura; they are small in size and gray in 
color; they communicate with the cerebro spinal nerves by two filaments, 
one of which is white, the other gray. 

The great splanchnic nerve is formed by the union of branches from the 
sixth, seventh, eighth and ninth ganglia; it passes through the diaphragm 
to the semilunar ganglion. 

The lesser splanchnic nerve is formed by the union of filaments from the 
tenth and eleventh ganglia, and is distributed to the coeliac plexus. 

The renal splanchnic nerve arises from the last thoracic ganglion an£ 
terminates in the renal plexus. 

The semilunar ganglia , the largest of the sympathetic, are situated by 
the side of the coeliac axis; they send radiating branches to form the solar 
plexus; from the various plexuses, nerves follow the gastric, splenic, 
hepatic, renal, etc., arteries, into the different abdominal viscera. 

The Lumbar Ganglia, four in number, are placed upon the bodies of 
the vertebrae; they give off branches which unite to form the aortic lumbar 
plexus and the hypogastric plexus, and follow the blood vessels to their 
terminations. 

The Sacral and Coccygeal Ganglia send filaments of distribution to 
all the blood vessels of the pelvic viscera. 

Properties and Functions. The sympathetic nerve possesses both 
sensibility and the power of exciting motion, but these properties are much 
less decided than in the cerebro-spinal system. Irritation of the ganglia 
does not produce any evidence of pain until some time has elapsed. If 
caustic soda be applied to the semilunar ganglia, or a galvanic current be 
passed through the splanchnic nerves, no instantaneous effect is noticed, as 
in the case of the cerebro-spinal nerves; but in the course of a few seconds 


150 


HUMAN PHYSIOLOGY. 


a slow, progressive contraction of the muscular coat of the intestines is 
established, which continues for some time after the irritation is removed. 
Division of the sympathetic nerve in the neck is followed by a vascular 
congestion of the parts above the section on the corresponding side, attended 
by an increase in the temperature; not only is there an increase in the 
amount of blood, but the rapidity of the blood current is very much hastened, 
and the blood in the veins becomes of a brighter color. Galvanization ot 
the upper end of the divided nerve causes all of the preceding phenomena 
to disappear; the congestion decreases, the temperature falls, and the venous 
blood becomes dark again. 

The sympathetic exerts a similar influence upon the circulation of the 
limbs and the glandular organs; destruction of the first thoracic ganglion 
and division of the nerves forming the lumbar and sacral plexuses, is fol¬ 
lowed by a dilatation of the vessels, an increased rapidity of the circulation, 
and an elevation of temperature in the anterior and posterior limbs; gal¬ 
vanization of the peripheral ends of these nerves causes all of these phe¬ 
nomena to disappear. Division of the splanchnic nerve causes a dilatation 
of the blood vessels of the intestine. 

These phenomena of the sympathetic nerve system are dependent upon 
the presence of vasomotor nerves, which, under normal circumstances, exert 
a tonic influence upon the blood vessels. These nerves, derived from the 
cerebro-spinal system, the medulla-oblongata, leave the spinal cord by the 
rami communicantes , enter the sympathetic ganglia, and finally terminate 
in the muscular wall of the blood vessels. 

Sleep is a periodical condition of the nervous system, in which there is 
a partial or complete cessation of the activities of the higher nerve centres. 
The cause of sleep is a diminution in the quantity of blood, occasioned by a 
contraction of the smaller arteries under the influence of the vasomotor nerves. 

During the waking state the brain undergoes a physiological waste, as 
a result of the exercise of its functions; after a certain length of time its 
activities become enfeebled, and a period of repose ensues, during which 
a regeneration of its substance takes place. 

When the brain becomes enfeebled there is a diminished molecular 
activity and an accumulation of waste products; under these circumstances 
it ceases to dominate the medulla oblongata and the spinal cord. These 
centres then act more vigorously, and diminish the calibre of the cerebral 
blood vessels through the action of the vasomoter nerves, producing a con¬ 
dition of physiological anaemia and sleep; during this state waste products 
are removed, force is stored up, nutrition is restored, and waking finally 
occurs. 


THE SENSE OF TOUCH. 


151 


THE SENSE OF TOUCH. 

The Sense of Touch is a modification of general sensibility, and 
located in the skin, which is especially adapted for this purpose, on account 
of the number of nerves and papillary elevations it possesses. The structures 
of the skin and the modes of termination of the sensory nerves have already 
been considered. 

The Tactile Sensibility varies in acuteness in different portions of the 
body; being most marked in those regions in which the tactile corpuscles 
are most abundant, e. g ., the palmar surface of the third phalanges of the 
fingers and thumb. 

The relative sensibility of different portions of the body has been ascer¬ 
tained by means of a pair of compasses, the points of which are guarded 
by cork, and then determining how closely they could be brought together, 
and yet be felt at two distinct points. The following are some of the 
rheasurements:— 


Point of tongue,.^ of a line. 

Palmar surface of third phalanx,.I line. 

Red surface of lips, .2 lines. 

Palmar surface of metacarpus,.3 “ 

Tip of the nose,. 3 “ 

Part of lips covered by skin,.4 “ 

Palm of hand,.5 “ 

Lower part of forehead,.10 “ 

Back of hand,.14 “ 

Dorsum of foot,. ... 18 “ 

Middle of the thigh,.30 “ 


The sense of touch communicates to the mind the idea of resistance only, 
and the varying degrees of resistance offered to the sensory nerves enable 
us to estimate, with the aid of the muscular sense, the qualities of hardness 
and softness of external objects. The idea of space or extension is obtained 
when the sensory surface or the external object changes its place in regard 
to the other, the character of the surface, its roughness or smoothness , is 
estimated by the impressions made upon the tactile papillae. 

Appreciation of Temperature. The general surface of the body is more 
or less sensitive to differences of temperature, though this sensation is 
separate from that of touch; whether there are nerves especially adapted 
for the conduction of this sensation has not been fully determined. Under 
pathological conditions, however, the sense of touch may be abolished, while 
the appreciation of changes in temperature may remain normal. 














152 


HUMAN PHYSIOLOGY. 


The cutaneous surface varies in its sensibility to temperature in different 
parts of the body, and depends, to some extent, upon the thickness of the 
skin, exposure, habit, etc.; the inner surface of the elbow is more sensitive 
to changes in temperature than the outer portion of the arm; the left hand 
is more sensitive than the right; the mucous membrane less so than the 
skin. 

Excessive heat or cold has the same effect upon the sensibility ; the tem¬ 
peratures most readily appreciated are those between 50° F. and 115 0 F. 

The sensations of pain and tickling appear to be conducted to the brain, 
also, by nerves different from those of touch; in abnormal conditions the 
appreciation of pain may be entirely lost, while touch remains unimpaired. 


THE SENSE OF TASTE. 

The Sense of Taste is localized mainly in the mucous membrane 
covering the superior surface of the tongue. 

The Tongue is situated in the floor of the mouth; its base is directed 
backward, and connected with the hyoid bone, by numerous muscles, with 
the epiglottis and soft palate; its apex is directed forward against the pos¬ 
terior surface of the teeth. 

The substance of the tongue is made up of intrinsic muscular fibres, the 
linguales; it is attached to surrounding parts, and its various movements 
performed by the extrinsic muscles, e. g., stylo-glossus, genio-hyo-glossus, 
etc. 

The mucous membrane covering the tongue is continuous with that lining 
the commencement of the alimentary canal, and is furnished with vascular 
and nervous papillae. 

The papillce are analogous in their structure to those of the skin, and 
are distributed over the dorsum of the tongue, giving it its characteristic 
roughness. 

There are three principal varieties:— 

1. Th z filiform papilla are most numerous, and cover the anterior two- 
thirds of the tongue; they are conical or filiform in shape, often prolonged 
into filamentous tufts, of a whitish color, and covered by horny epithelium. 

2. The fungifomn papillce are found chiefly at the tip and sides of the 
tongue; they are larger than the preceding, and may be recognized by 
their deep red color. 

3. The circumvallate papilla are rounded eminences, from eight to ten 
in number, situated at the base of the tongue, where they form a V-shaped 


THE SENSE OF TASTE. 


153 


figure. They are quite large, and consist of a central projection of mucous 
membrane, surrounded by a wall, or circumvallation, from which they 
derive their name. 

The Taste Beakers, supposed to be the true organs of taste, are flask¬ 
like bodies, ovoid in form, about of an inch in length, situated in 
the epithelial covering of the mucous membrane, on the circumvallate 
papillae. They consist of a number of fusiform, narrow cells, and curved 
so as to form the walls of this flask-like body; in the interior are elongated 
cells, with large, clear nuclei, the taste cells. 

Nerves of Taste. The chorda tympani nerve, a branch of the facial, 
after leaving the cavity of the tympanum, joins the 3d division of the 5th 
nerve between the two pterygoid muscles, and then passes forward in the 
lingual branches, to be distributed to the mucous membrane of the anterior 
two-thirds of the tongue. Division or disease of this nerve is followed by 
a loss of taste in the part to which it is distributed. 

The glosso-pharyngeal enters the tongue at the posterior border of the 
hyo-glossus muscle, and is distributed to the mucous membrane of the base 
and sides of the tongue, fauces, etc. 

The lingual branch of the trifacial nerve endows the tongue with gen¬ 
eral sensibility; the hypoglossal endows it with motion. 

The nerves of taste in the superficial layer of the mucous membrane 
form a fine plexus, from which branches pass to the epithelium and pene¬ 
trate it; others enter the taste beakers, and are directly connected with the 
taste cells. 

The seat of the sense of taste has been shown by experiment to be the 
whole of the mucous membrane over the dorsum of the tongue, soft palate, 
fauces, and upper part of the pharynx. 

The Sense of Taste enables us to distinguish the savor of substances 
introduced into the mouth, which is different from tactile sensibility. The 
sapid quality of substances appreciated by the tongue are designated as 
bitter, sweet, alkaline, sour, salt, etc. 

The Essential Conditions for the production of the impressions of 
taste are (1) a state of solubility of the food; (2) a free secretion of the 
saliva, and (3) active movements on the part of the tongue, exciting pres¬ 
sure against the roof of the mouth, gums, etc., thus aiding the solution of 
various articles and their osmosis into the lingual papillae. Sapid substances, 
when in a state of solution, pass into the interior of the taste beakers, and 
come into contact, through the medium of the taste cells, with the terminal 
filaments of the gustatory nerves. 

K 


154 


HUMAN PHYSIOLOGY. 


THE SENSE OF SMELL. 

The Sense of Smell is located in the mucous membrane lining the 
upper part of the nasal cavity, in which the olfactory nerves are distributed. 

The Nasal Fossae are two cavities, irregular in shape, separated by 
the vomer, the perpendicular plate of the ethmoid bone, and the triangular 
cartilage. They open anteriorly and posteriorly by the anterior and pos¬ 
terior nares, the latter communicating with the pharynx. They are lined 
by mucous membrane, of which the only portion capable of receiving 
odorous impressions is the part lining the upper one-third of the fossae. 

The Olfactory Nerves, arising by three roots from the posterior and 
inferior surface of the anterior lobes, pass forward to the cribriform plate 
of the ethmoid bone, where they each expand into an oblong body, the 
olfactory bulb. From its under surface from fifteen to twenty filaments pass 
downward through the foramina, to be distributed to the olfactory mucous 
membrane, where they terminate in long, delicate, spindle-shaped cells, 
the olfactory cells , situated between the ordinary epithelial cells. 

The olfactory bulbs are the centres in which odorous impressions are 
perceived as sensations; destruction of these bulbs being attended by an 
abolition of the sense of smell. 

In animals which possess an acute sense of smell, there is a correspond¬ 
ing increase in the development of the olfactory bulbs. 

The Essential Conditions for the sense of smell are, (i) a special 
nerve centre capable of receiving impressions and transforming them into 
.odorous sensations. (2) Emanations from bodies which are in a gaseous 
or vaporous condition. (3) The odorous emanations must be drawn freely 
through the nasal fossae; if the odor be very faint, a peculiar inspiratory 
movement is made, by which the air is forcibly brought into contact with 
the olfactory filaments. The secretions of the nasal fossae probably dissolve 
the odorous particles. 

Various substances, as ammonia, horseradish, etc., excite the sensibility 
of the mucous membrane, which must be distinguished from the perception 
of true odors. 


THE SENSE OF SIGHT. 

The Eyeball. The eyeball or organ of vision is situated at the fore 
part of the orbital cavity and supported by a cushion of fat; it is protected 
from injury by the bony walls of the cavity, the lids and lashes, and is so 


THE SENSE OF SIGHT. 


155 


situated as to permit of an extensive range of vision. The eyeball is loosely 
held in position by a fibrous membrane, the capside of Tenon , which is 
attached on the one hand to the eyeball itself and on the-other to the walls 
of the cavily. Thus suspended, the eyeball is capable of being moved in 
any direction by the contraction of the muscles attached to it. 

Structure. The eyeball is spheroidal in shape and measures about nine- 
tenths of an inch in its antero-posterior diameter, and a little less in its 
transverse diameter. When viewed in profile it is seen to consist of the 
segments of two spheres, of which the posterior is the larger, occupying 
five-sixths, and the anterior the smaller, occupying one-sixth of the ball. 

The eye is made up of several membranes concentrically arranged, within 
which are enclosed the refracting media essential to vision. These mem¬ 
branes enumerated from without inwards, are : 1st, the sclerotic and cornea; 
2d, the choroid and iris; 3d, the retina; the refracting media are the 
aqueous humor, the crystalline lens and vitreous humor. 

The Sclerotic and Cornea. The sclerotic is the opaque fibrous mem¬ 
brane covering the posterior five-sixths of the ball. It is composed of con¬ 
nective tissue arranged in layers which run both transversely and longitudi¬ 
nally; it is pierced posteriorly by the optic nerve about one-tenth of an 
inch internal to the optic axis. The sclerotic by its density gives form to 
the eye and protects the delicate structures within it, and serves for the 
attachment of the muscles by which the ball is moved. 

The cornea is a transparent non-vascular membrane covering the anterior 
one-sixth of the eyeball. It is nearly circular in shape and is continuous at 
the circumference with the sclerotic, from which it cannot be separated. 
The substance of the cornea is made up of thin layers of delicate trans¬ 
parent fibrils of connective tissue more or less united together; between 
these layers are found a number of inter-communicating lymph spaces lined 
by endothelium, which are in connection with lymphatics. Leucocytes or 
lymph corpuscles are often found in these spaces. The anterior surface of 
the cornea is covered by several layers of nucleated epithelium which rest 
upon a structureless membrane known as the anterior elastic lamina. The 
posterior surface is covered by a similar membrane, the membrane of 
Decemet, which becomes continuous at its periphery with the iris; it is also 
covered by a layer of epithelial cells. At the junction of the cornea and 
sclerotic is found a circular groove, the canal of Schlemm. 

The Choroid, the Iris, the Ciliary Muscle and Ciliary processes, 
together constitute the second or middle coat of the eyeball. 

The choroid is a dark brown membrane which extends forward nearly 


156 


HUMAN PHYSIOLOGY. 


to the cornea, where it terminates in a series of folds, the ciliary processes. 
In its structure the choroid is highly vascular, consisting^ both arteries and 
veins. Externally it is connected with the sclerotic by connective tissue; 
internally it is lined by a layer of hexagonal pigment cells which, though 
usually classed as belonging to the choroid, is now known to belong embryo- 
logically and physiologically to the retina. From without inward may be 
distinguished the following layers :— 

1. The lamina supra-choroidea. 

2. The elastic layer of Sattler, consisting of two endothelial layers. 

3. The chorio-capillaris, choroid proper, or membrane of Ruysch, a 

thick elastic network of arterioles and capillaries lying within the 
outer layer of veins and arteries called the vena vorticosae. 

4. The lamina vitrea or internal limiting membrane. 

The choroid with its contained blood vessels bears an important relation to 
the nutrition of the eye; it provides for the blood supply, for drainage from 
the body of the eye, and presents an uniform and high temperature to the 
retina. 

The Iris is the circular variously-colored membrane placed in the an¬ 
terior portion of the eye just behind the cornea. It is perforated a little to 
the nasal side of the centre by a circular opening, the pupil. The outer 
or circumferential border is connected with the cornea, ciliary muscle and 
ciliary processes; the free inner edge forms the boundary of the pupil, the 
size of which is constantly changing. The framework of the iris is com¬ 
posed of connective tissue, blood vessels, muscular fibres and pigmented 
connective-tissue corpuscles. The anterior surface is covered with a layer 
of epithelial cells continuous with those covering the posterior surface of 
the cornea; the posterior surface is lined by a limiting membrane bearing 
pigment epithelial cells continuous with those of the choroid. The various 
colors which the iris assumes in different individuals depend upon the 
quantity and disposition of the pigmentary granules. 

The muscular fibres of the iris, which are of the non-striated variety, are 
arranged in two sets,—the sphincter and dilator. 

The sphincter pupillce is a circular flat band of muscular fibres surround¬ 
ing the pupil close to its posterior surface; by its contraction and relaxa¬ 
tion, the pupil is diminished or increased in size. The dilator pupillce 
consists of a thin layer of fibres arranged in a radiate manner; at the mar¬ 
gin of the pupil they blend with those of the sphincter muscle, while at the 
outer border they arch to form a circular muscular layer. 

The ciliary muscle is a gray circular band consisting of unstriped muscu¬ 
lar fibres about one-tenth of an inch long running from before backward. 


THE SENSE OF SIGHT. 


157 


It is attached anteriorly to the inner surface of the sclerotic and cornea, 
and posteriorly to the choroid coat opposite the ciliary processes. At the 
anterior border of the radiating fibres and internally are found bundles of 
circular muscular fibres, constituting the annular muscle of Muller. The 
ciliary muscle thus consists of two sets of fibres, a radiating and circular, 
both of which are concerned in effecting a change in the convexity of the 
lens in the accommodation of the eye to near vision. 

The Retina forms the internal coat of the eye. In the fresh state it is a 
delicate transparent membrane of a pink color, but after death soon becomes 


Fig. 20. 



SCLEROTIC COAT REMOVED TO SHOW THE CHOROID, CILIARY MUSCLE AND NERVES. 

a. Sclerotic coat. b. Veins of the choroid, c. Ciliary nerves, d. Veins of the choroid. 
e. Ciliary muscle, f Iris .—From Holden’s Anatomy. 


opaque; it extends forward almost to the ciliary processes, where it termi¬ 
nates in an indented border, the ora serrata. In the posterior part of the 
retina at a point corresponding to the axis of vision is a yellow spot, the 
macula lutea> which is somewhat oval in shape and tinged with yellow 
pigment. It presents in its centre a depression, the fovea centralis , corres¬ 
ponding to a decrease in thickness of the retina; about one-tenth of an 
inch to the inner side of the macula is the point of entrance of the optic 
nerve. The arleria centralis retince pierces the optic nerve near the 
sclerotic, runs forward in its substance and is distributed in the retina as far 
forward as the ciliary processes. 










158 


HUMAN PHYSIOLOGY. 


The retina is remarkably complex, consisting of ten distinct layers, from 
within outward, supported by connective tissue. These are as follows, 
viz.: I. Membrana limitans interna. 2. Fibres of optic nerve. 3. 
Layers of ganglionic corpuscles, 4. Molecular layer. 5 - Internal granu¬ 
lar layer. 6. Molecular layer. 7. External granular layer. 8. Mem¬ 
brana limitans externa. 9. Jacobson’s membrane or layer of rods and cones. 
10. The layer of pigment cells. 

The most important of these, however, is the layer of rods and cones in 
the external portion of the retina. The rods are straight elongated cylinders 
extending through the entire thickness of Jacobson’s membrane. They 
consist of an external portion which is clear, homogeneous and highly re¬ 
fracting, and of an internal portion which is slightly granular and less 
refractive; the outer end of each rod is in direct contact with the pig¬ 
mentary epithelium lining the choroid, while the inner end tapering to a fine 
thread, pierces the external limiting membrane and passes into the external 
granular layer. The cones consist also of two portions, the inner of which 
is somewhat thicker than the rod and rests upon the limiting membrane; 
the outer portion tapers to a fine point which is known as the cone-style. 
The cones, as a rule, are somewhat shorter than the rods. The propor¬ 
tion of rods to cones varies in different parts of the retina, though there are 
on the average about fourteen rods to one cone. In the macula lutea, where 
vision is most acute, the rods are almost entirely absent, cones alone being 
present. All the retinal elements at this point are changed. The nerve 
fibre layer is absent, the axis cylinders radiating in such a manner as to 
leave the spot free from their covering. The remaining layers are all 
thinned and the stroma reduced to a minimum. The optic nerve after 
passing forward from the brain penetrates in succession the sclerotic, 
choroid, and retina ; the nerve fibres then spread out over the anterior 
surface of the retina and become connected with the large ganglionic cells, 
the third layer of the retina. 

The number of optic nerve fibres in the retina is estimated to be about 
800,000, and for each fibre there are about seven cones, one hundred rods, 
and seven pigment cells. The points of the rods and cones are directed 
toward the choroid, or away from the entering light, and dip into the pig¬ 
mentary layer. They, with the pigment layer, are the elements interme¬ 
diating the change of the ethereal vibrations into nerve force; out of these 
nerve vibrations the brain fashions the sensations of light, form and color. 

The vitreous humor , which supports the retina, is the largest of the re¬ 
fracting media; it is globular in form and constitutes about four-fifths of the 
ball; it is hollowed out anteriorly for the reception of the crystalline lens. 


THE SENSE OF SIGHT. 


159 


The outer surface of the vitreous is covered by a delicate transparent mem¬ 
brane, termed the hyaloid membrane , which serves to maintain its globular 
form. 

The aqueous humor found in the anterior chamber of the eye is a clear 
alkaline fluid, having a specific gravity of 1.003-1.009. It is secreted most 
probably by the blood vessels of the iris and ciliary processes. It passes 
from the interior of the eye, through the canal of Schlemm and the meshes 
at the base of the iris, into the anterior circular vein. 

The crystalline lens enclosed within its capsule, is a transparent bi-con- 
vex body, situated just behind the iris and resting in the depression in the 
anterior part of the vitreous. The two convexities are not quite alike, the 
curvature of the posterior surface being slightly greater than that of the an¬ 
terior. The lens measures about one-third of an inch in the transverse 
diameter and one-fifth of an inch in the antero-posterior diameter. 

The suspensory ligament , by which the lens is held in position, is a firm 
transparent membrane, united to the ciliary processes. A short distance 
beyond its origin, it splits into two layers, the anterior of which is inserted 
into the capsule of the lens and blends with it; the posterior passing inward 
behind the lens, becomes united to its capsule. The anterior layer pre¬ 
sents a series of foldings, Zone of Zinn, which are inserted into the intervals 
of the folds of the ciliary processes. The triangular space between the two 
layers is the canal of Petit. 

Blood vessels and Nerves. The structures composing the eyeball are 
supplied with blood by the long and short ciliary arteries, branches of the 
ophthalmic; they pierce the sclerotic at various points and are ultimately 
distributed to all tissues within the ball. 

The nerve supply comes largely from the ophthalmic or ciliary ganglion. 
This is a small body, situated in the posterior part of the orbit; it receives 
motor fibres from a branch of the motor-oculi, or third nerve; a sensory 
branch from the ophthalmic division of the fifth nerve and fibres from the 
cavernous plexus of the sympathetic. From the anterior border of the 
ganglion proceed the ciliary nerves which, entering the eyeball, endow its 
structures with motion and sensation. 

The Eyeball a Living Camera Obscura. The eyeball may be com¬ 
pared in a general way to a camera obscura. The anatomical arrangement 
of its structures reveal many points of similarity. The sclerotic and choroid 
may be compared with the walls of the chamber; the combined refractive 
media, cornea, aqueous humor, lens, and vitreous humor, to the lens for 
focusing the rays of light; the retina to the sensitive plate receiving the 


160 


HUMAN PHYSIOLOGY. 


image formed at the focal point; the iris to the diaphragm, which by cutting 
off the marginal rays prevents spherical aberration and. at the same time 
regulates the amount of light entering the eye; the ciliary muscle to the 
adjusting screw by which distinct images are thrown upon the retina in spite 
of varying distances of the object from which the light rays emanate. The 
structures just enumerated are those essential for normal vision. 

The relationship of the various structures composing the eyeball is shown 
by the following figure :— 


Fig. 21. 



DIAGRAM OF A VERTICAL SECTION OF THE EYE. 
i. Anterior chamber filled with aqueous humor. 2. Posterior Chamber. 3. Canal o* 

Petit. 

a. Hyaloid membrane, b. Retina (dotted line), c. Choroid coat (black line). 
d. Sclerotic coat. e. Cornea, f. Iris. g. Ciliary processes, h. Canal of Schlemm 
or Fontana, i. Ciliary muscle .—From Holden’s Anatomy. 

The Dioptric or Refracting apparatus by which the rays of light enter¬ 
ing the eye are so manipulated as to produce an image on the retina, 
consists of the cornea, aqueous humor, crystalline lens and vitreous humor. 
A ray of light in passing through each of these media will undergo refrac¬ 
tion at their surfaces and ultimately be brought to a focus at the retina. 
Inasmuch as the two surfaces of the cornea are parallel and its refractive 
power practically the same as the aqueous humor, the media may be re¬ 
duced to three, viz: 1. Cornea and aqueous humor. 2. The lens. 3. 
The vitreous humor. The refracting surfaces may also be reduced to three, 
















THE SENSE OF SIGHT. 


161 


viz: i. Anterior surface of the cornea. 2. Anterior surface of lens. 3. 
Posterior surface of lens. 

The refraction effected by the cornea is very great, owing to the passage 
of the light from the air into a comparatively dense medium, and is sufficient 
of itself to bring parallel rays of light to a focus about 10 millimetres behind 
the retina. This would be the condition in an eye in which the lens was 
congenitally absent. Perfect vision requires, however, that the convergence 
of the light shall be great enough that the image may fall upon the retina. 
This is accomplished by the crystalline lens, a body denser than the cornea 
and possessing a higher refractive power. The manner in which a biconvex 
lens focuses both parallel and divergent rays is shown in the following 
figures:— 

Fig. 22. 



DIAGRAM SHOWING THE COURSE OF PARALLEL RAYS OF LIGHT FROM A IN THEIR PASSAGE 
THROUGH A BICONVEX LENS L, IN WHICH THEY ARE SO REFRACTED AS TO BEND 

TOWARD AND come to A focus at a point F .—From Yeo’s Text-Book of Physiology. 


Fig. 23. 



DIAGRAM SHOWING THE COURSE OF DIVERGING RAYS WHICH ARE BENT TO A POINT 
FURTHER FROM THE LENS THAN THE PARALLEL RAYS IN PRECEDING FIGURE .—Prom 

Yl'o’s Text-Book of Physiology. 


The function of the crystalline lens, therefore, is to focus the rays of light 
with the formation of an image on the retina. 

The Retinal Image corresponds in all respects to the object from which 
the light proceeds. The existence of this image can be demonstrated by 
removing from the eye of a recently killed animal a circular portion of the 
sclerotic and choroid posteriorly and then placing at the proper distance in 
front of the cornea a lighted candle ; an inverted image of the candle will be 














162 


HUMAN PHYSIOLOGY. 


seen upon the retina. The size of the retinal image depends upon the 
visual angle, which in turn depends upon the size of the object and its 
distance from the eye. At a distance of 15.2596 metres the image of an 
object 1 metre high would be 1 millimetre, or a thousand times smaller than 
the object. 

Accommodation. By accommodation is understood the power which 
the eye possesses of adjusting itself to vision at different distances. In a 
normal or emmetropic eye parallel rays of light are brought to a focus on 
the retina; but divergent rays, that is rays coming from a near luminous 
point, will be brought to a focus behind the retina, provided the refractive 
media remain the same; as a result vision would be indistinct, from the 
formation of diffusion circles. It is impossible to see distinctly, therefore, 
a near and distant object at the same time. We must alternately direct 
the vision from one to the other. A normal eye does not require adjust¬ 
ing for parallel rays; but for divergent rays a change in the eye is necessi¬ 
tated ; this is termed accommodation. In the accommodation for near 
vision the lens becomes more convex, particularly on its anterior surface ; 
the increase in convexity increases its refractive power; the greater the 
degree of divergence of the rays previous to entering the eye, the greater 
the increase of convexity of the lens and convergence of the rays after 
passing through it. By this alteration in the shape of the lens we are 
enable to focus light rays coming from, and to see distinctly, near as well 
as distant objects. 

Function of the Ciliary Muscle. Though it is admitted that the 
change in the convexity of the lens is caused by the contraction of the 
ciliary muscle and the relaxation of the suspensory ligament, the exact manner 
in which it does so is not understood. When the eye is in repose as in 
distant vision, the suspensory ligament is tense and the lens possesses that 
degree of curvature necessary for focusing parallel rays. In the voluntary 
efforts to accommodate the eye for near vision, the ciliary muscle contracts, 
the suspensory ligament relaxes and the lens, inherently elastic, bulges for¬ 
ward and once again focuses the rays upon the retina. It is, therefore, 
termed the muscle of accommodation, and by its alternate contraction and 
relaxation the lens is rendered more or less convex, according to the 
requirements for near and distant vision. 

Range of accommodation. Parallel rays coming from a luminous 
point, distant not less than 200 feet, do not require adjustment: from this 
point up to infinity no accommodation is required for perfect vision. This 
is termed the punctum remotion, and indicates the distance to which an object 


THE SENSE OF SIGHT. 


163 


may be removed and yet distinctly seen. If the object be brought nearer 
to the eye than 200 feet the accommodative power must come into play : 
the nearer the object the more energetic must be the contraction of the 
ciliary muscle and the consequent increase in the convexity of the lens. At 
a distance of five inches, however, the power of accommodation reaches its 
maximum : this is termed the punctum proximum, and indicates the nearest 
point at which an object may be seen distinctly. The distance between 
these two points is the range of accommodation. 

Optical Defects. Astigmatism is a condition of the eye which 
prevents vertical and horizontal lines from being focused at the same 
time, and is due to a greater curvature of the cornea in one meridian 
than another. 

Spherical aberration is a condition in which there is an indistinctness of 
an image from the unequal refraction of the rays of light passing through 
the circumference and the centre of the lens; it is corrected mainly by the 
iris, which cuts off the marginal rays; and only transmits those' passing 
through the centre. 

Chromatic aberration is a condition in which the.image is surrounded by 
a colored margin, from the decomposition of the rays of light into their 
elementary parts. 

Myopia , or short-sightedness , is caused by an abnormal increase in the 
antero-posterior diameter of the eyeball, or by a subnormal refracting power 
of the lens; it is generally due to the first cause; the lens being too far 
removed from the retina, forms the image in front of it, and the perception 
becomes dim and blurred. Concave glasses correct this defect, by prevent¬ 
ing the rays from converging too soon. 

Hypermetropia , or long-sightedness , is caused by a shortening of the 
antero-posterior diameter, or by an excessive refractive power of the lens; 
the focus of the rays of light would, therefore, be behind the retina. Con¬ 
vex glasses correct this defect, by converging the rays of light more anteri¬ 
orly. 

Presbyopia is a loss of the power of accommodation of the eye to near 
objects, and usually occurs between the ages of 40 and 60; it is remedied by 
the use of convex glasses. 

The Iris. The iris plays the part of a diaphragm, and by means of its 
central aperture the pupil regulates the quantity of light entering the 
interior of the eye; by preventing rays from passing through the margin of 
the lens it diminishes spherical aberration. The size of the pupil depends 
upon the relative degree of contraction of the circular and radiating fibres; 


164 


HUMAN PHYSIOLOGY. 


the variations in size of the pupil from variations in the degree of contrac¬ 
tion depend upon different intensities of light. If the light be intense the 
circular fibres contract and diminish the size of the pupil; if the light 
diminishes in intensity the circular fibres relax and the pupil enlarges. 

Point of most distinct Vision. While all portions of the retina are 
sensitive to light, their sensibility varies within wide limits. At the macula 
lutea and more especially in its most central depression, the fovea, where 
the retinal elements are reduced practically to the layer of rods and cones, 
the sensibility reaches its maximum. It is at this point that the image is 
found when vision is most distinct. The macula and fovea are always in 
the line of direct vision. From the macula towards the periphery of the 
retina there is a gradual diminution in sensibility and a corresponding decline 
in the distinctness of vision. In those portions of the retina lying outside 
the macula, the indistinctness of vision depends not only on diminished 
sensibility, but also upon inaccurate focusing of the rays. 

Blind Spot. Although the optic nerve transmits the impulses excited 
in the retina by the ethereal vibration, the nerve fibres themselves are insen¬ 
sitive to light. At the point of entrance of the optic nerve, owing to the 
absence of the rods and cones, the rays of light make no impression. This 
is the blind spot. As this spot is not in the line of vision, no dark point is 
ordinarily observed in the field of vision, that circular space before a fixed 
eye within which objects are perceptible. 

The rods and cones are the most sensitive portions of the retina. A ray 
of light entering the eye passes entirely through the various layers of the 
retina and is arrested only upon reaching the pigmentary epithelium in 
which the rods and cones are imbedded. As to the manner in which the 
objective stimuli, light and color so-called, are transformed into nerve im¬ 
pulses, but little is known. It is probable that the ethereal vibrations are 
transformed into heat, which excites the rods and cones. These acting as 
highly specialized end organs of the optic nerve, start the impulses on their 
way to the brain where the seeing process takes place. As to the relative 
function of the rods and cones, it has been suggested, from the study 
of the facts of comparative anatomy, that the rods are impressed only by 
differences in the intensity of light, while the cones in addition are im¬ 
pressed by qualitative differences or color. 

Accessory Structures. The muscles which move the eyeball are six 
in number; the superior and inferior recti, the external and internal recti, 
the superior and inferior oblique muscles. The four recti muscles, arising 
from the apex of the orbit, pass forward and are inserted into the sides of 


THE SENSE OF HEARING. 


165 


the sclerotic coat; the superior and inferior muscles rotate the eye around 
a horizontal axis; the external and internal rotate it around a vertical 
axis. 

The Superior oblique muscle, having the same origin, passes forward to 
the inner and upper angle of the orbital cavity, where its tendon passes 
through a cartilaginous pulley; it is then reflected backward and inserted 
into the sclerotic just behind the transverse diameter. Its function is to 
rotate the eyeball in such a manner as to direct the pupil downward and 
outward. 

The Inferior oblique muscle arises at the inner angle of the orbit and 
then passes outward and backward, to be inserted into the sclerotic. Its 
function is to rotate the eyeball and direct the pupil upward and outward. 

By the associated action of all these muscles, the eyeball is capable of 
performing all the varied and complex movements necessary for distinct 
vision. 

The Eyelids , bordered with short, stiff hairs, shade the eye and protect 
it from injury. On the posterior surface, just beneath the conjunctiva, are 
the Meibomian glands, which secrete an oily fluid; it covers the edge of 
the lids, and prevents the tears from flowing over the cheek. 

The Lachrymal Glands are ovoid in shape, and situated at the upper 
and outer part of the orbital cavity; they open by from six to eight ducts 
at the outer portion of the upper lids. 

The Tears , secreted by the lachrymal glands, are distributed over the 
cornea by the lids during the act of winking, and keep it moist and free 
from dust. The excess of tears passes into the lachrymal ducts, which 
begin by two minute orifices, one on each lid, at the inner canthus. They 
conduct the tears into the nasal duct, and so into the nose. 


THE SENSE OF HEARING. 

The Ear or Organ of Hearing is lodged within the petrous portion 
of the temporal bone. It may be, for convenience of description, divided 
into three portions, viz: i. The external ear. 2. The middle ear. 3. 
The internal ear or labyrinth. 

The External Ear consists of the pinna or auricle and the external au¬ 
ditory canal. The pinna consists of a thin layer of cartilage, presenting a 
series of elevations and depressions; it is attached by fibrous tissue to the 
outer bony edge of the auditory canal; it is covered by a layer of integu¬ 
ment continuous with that covering the side of the head. The general 


166 


HUMAN PHYSIOLOGY. 


shape of the pinna is concave and presents a little below the centre a deep 
depression, the concha. The external auditory canal extends from the 
concha inward for a distance of about one and a quarter inches. It is 
directed somewhat forward and upward, passing over a convexity of bone, 
and then dips downward to its termination; it is composed of both bone 
and cartilage and lined by a reflection of the skin covering the pinna. At 
the external portion of the canal the skin contains a number of tubular 
glands, the ceruminous glands , which in their conformation resemble the 
perspiratory glands. They secrete the cerumen or ear wax. 

The Middle Ear or Tympanum is an irregularly shaped cavity hollowed 
out of the temporal bone and situated between the external ear and the 
labyrinth. It is narrow from side to side but relatively long in its vertical 
and antero posterior diameters; it is separated from the external auditory 
canal by a membrane, the membrana tympani ; from the internal ear it is 
separated by an osseo-membranous partition which forms a common wall for 
both cavities. The middle ear communicates posteriorly with the mastoid 
cells, anteriorly with the naso-pharynx by means of the Eustachian tube. 
The interior of this cavity is lined by mucous membrane continuous 
with that lining the pharynx. 

The membrana tympani is a thin, translucent, nearly circular membrane, 
measuring about two-fifths of an inch in diameter, placed at the inner ter¬ 
mination of the external auditory canal. The membrane is enclosed within 
a ring of bone which, in the foetal condition, can be easily removed, but in 
the adult condition becomes consolidated with the surrounding bone. The 
membrana tympani consists primarily of a layer of fibrous tissue, arranged 
both circularly and radially, and forms the membrana propria ; externally, 
it is covered by a thin layer of skin continuous with that lining the auditory 
canal; internally, it is covered by a thin mucous membrane. The tympanic 
membrane is placed obliquely at the bottom of the auditory canal, inclining 
at an angle of 45 0 , being directed from behind and above downward and 
inward. On its external surface this membrane presents a funnel-shaped 
depression, the sides of which are somewhat convex. 

The Ear-bones. Running across the tympanic cavity and forming an 
irregular line of jointed levers, is a chain of bones which articulate with 
each other at their extremities. They are known as the malleus, incus and 
stapes. 

The form and position of these bones are shown in Fig. 24. 

The malleus consists of a head, neck and handle, of which the latter is 
attached to the inner surface of the membrana tympani; the incus t or anvil 


THE SENSE OF HEARING. 


167 


bone presents a concave, articular surface, which receives the head of the 
malleus; the stapes , or stirrup bone, articulates externally with the long pro¬ 
cess of the incus, and internally, by its oval base, with the edges of the fora¬ 
men ovale. 

The tensor tympani muscle consists of a fleshy, tapering portion, half 
an inch in length, which terminates in a slender tendon; it arises from the 


Fig. 24. 



TYMPANUM AND AUDITORY OSSICLES (LEFT) MAGNIFIED. 

A.G., external meatus; M, membrana tympani, which is attached to the handle of the 
malleus, n, and near it the short process, /; h, head of the malleus; a, incus ; k, its 
short process with its ligament; long process; s, Sylvian ossicle; S, stapes; Ax, 
Ax, is the axis of rotation of the ossicles; it is shown in perspective, and must be 
imagined to penetrate the plane of the paper; t, line of traction of the tensor tympani. 
The other arrows indicate the movement of the ossicles when the tensor contracts. 


cartilaginous portion of the Eustachian tube and adjacent surface of the 
sphenoid bone. From this origin the muscle passes nearly horizontally 
backward to the tympanic cavity; just opposite to the fenestra ovalis its 
tendon bends at a right angle over the processus cochleariformis and then 
passes outward across the cavity to be inserted into the handle of the mal¬ 
leus near the neck. 


168 


HUMAN PHYSIOLOGY. 


The stapedius muscle emerges from the cavity of a pyramid of bone 
projecting from the posterior wall of the tympanum; the tendon passes 
forward and is inserted into the neck of the stapes bone posteriorly near its 
point of articulation with the incus. 

The laxator tympani muscle, so-called, is now generally regarded as liga¬ 
mentous in nature, and not muscular. 

The Eustachian tube, by means of which a free communication is 
established between the middle ear and pharynx, is partly bony and partly 
cartilaginous in structure. It measures about an inch and a half in length; 
commencing at its opening into the naso-pharynx it passes upward and out¬ 
ward to the spine of the sphenoid bone, at which point it becomes some¬ 
what contracted; the tube then dilates as it passes backward into the middle 
ear cavity; it is lined by mucous membrane, which is continued into the 
middle ear and mastoid cells. 

The Function of the Ear, as a whole, is the reception and transmis¬ 
sion of aerial vibrations to the terminal organs concealed within the in¬ 
ternal ear and which are connected with the auditory nerve fibres. The 
excitation of these end organs caused by the impact of the vibrations, 
arouses in the auditory nerve impulses which are then transmitted to the 
brain, where the hearing process takes place. In order to appreciate the 
functions of the individual parts of the ear a few of the characteristics 
of sound waves must be kept in mind. 

Sound Waves. All sounds are caused by vibrations in the atmosphere 
which have been communicated to it by vibrating elastic bodies, such as 
membranes, strings, rods, etc. These vibrating bodies produce in the air 
a to and fro movement of its particles, resulting in a series of alternate 
condensations and rarefactions which are propagated in all directions. A 
complete oscillation of a particle of air forward and backward constitutes a 
sound-wave. Musical sounds are caused by a succession of regular waves 
which follow each other with a certain rapidity. Noises are caused by the 
impact of a series of irregular waves. 

All sound waves possess intensity, pitch, and quality. The intensity , or 
loudness, of a sound depends upon the amplitude of the vibration, or the 
extent of its excursion. The pitch depends upon the number of vibrations 
which affect the auditory nerve in a second of time ; the pitch of the note 
C, the first below the leger line of the musical scale, is caused by 256 
vibrations per second ; the pitch of the same note an octave higher is 
caused by 512 vibrations per second. If the vibrations are too few per 
second they fail to be perceived as a continuous sound; the minimum 


THE SENSE OF HEARING. 


169 

number of vibrations capable of producing a sound has been fixed at 16 per 
second ; the highest pitched musical note capable of being heard has been 
shown to be due to 38,000 vibrations per second. In the ascent of the 
musical scale there is, therefore, a gradual increase in the number of vibra¬ 
tions and a gradual increase in the pitch of the sounds. Between the two 
extreme limits lies the range of audibility, which embraces eleven octaves, 
of which seven are employed in the musical scale. 

The quality of sound depends upon a combination of the fundamental 
vibration with certain secondary vibrations of sub-divisions of the vibrating 
body. These so-called over-tones vary in intensity and pitch, and by 
modifying the form of the primary wave produce that which is termed 
the quality of sound. 

Function of the Pinna and External Auditory Canal. In those 
animals possessing movable ears, the pinna plays an important part in the 
collection of sound-waves. In man, in whom the. capability of moving the 
pinna has been lost, it is doubtful if it is at all necessary for hearing. Never¬ 
theless an individual with dull hearing may have the perception of sound 
increased by placing the pinna at an angle of 45 0 to the side of the head. 
The external auditory canal transmits the sonorous vibrations to the tym¬ 
panic membrane. Owing to the obliquity of this canal it has been sup¬ 
posed that the waves, concentrated at the concha, undergo a series of re¬ 
flections on their way to the tympanic membrane, and, owing to the 
position of this membrane, strike it almost perpendicularly. 

Function of the Tympanic Membrane. The function of the tym¬ 
panic membrane appears to be the reception of sound vibrations by being 
thrown by them into reciprocal vibrations which correspond in intensity and 
amplitude. That this membrane actually reproduces all vibrations within 
the range of audibility has been experimentally demonstrated. The mem¬ 
brane not being fixed, as far as its tension is concerned, does not possess a 
fixed fundamental note, like a stationary fixed membrane, and is therefore 
just as well adapted for the reception of one set of vibrations as another. 
This is made possible by variations in its tension in accordance with the 
pitch of the sounds. In the absence of all sound the membrane is in a 
condition of relaxation ; with the advent of sound-waves possessing a 
gradual increase of pitch, as in the ascent of the musical scale, the tension 
of the tympanic membrane is gradually increased until its maximum ten¬ 
sion is reached at the upper limit of the range of audibility. By this 
change in tension certain tones become perceptible and distinct, while 
others become indistinct and inaudible. 


L 


170 


HUMAN PHYSIOLOGY. 


Function of the Tensor Tympani Muscle. The function of this 
muscle is, as its name indicates,.to increase the tension of the membrane in 
accordance with the pitch of the sound wave. The tendon of this muscle 
playing over the processus cochleariformis and attached at almost a right 
angle to the handle of the malleus, will, when the muscle contracts, pull 
the handle inwards, increase the convexity of the membrane, and at the 
same time increase its tension; with the relaxation of this muscle, the handle 
of the malleus passes outward and the tension is diminished. The contractions 
of the tensor muscle are reflex in character and excited by nerve impulses 
reaching it through the small petrosal nerve and otic ganglion. The number 
of nerve stimuli passing to the muscle and determining the degree of con¬ 
traction will depend upon the pitch of the sound wave and the subsequent 
excitation of the auditory nerve. The tensor tympani muscle may be re¬ 
garded as an accommodative apparatus by which the tympanic membrane is 
adjusted to enable it to receive vibrations of varying degrees of pitch. 

Function of the Ossicles. The function of the chain of bones is to 
transmit the sound waves across the tympanic cavity to the internal ear. 
The first of these bones, the malleus, being attached to the tympanic mem¬ 
brane will take up the vibrations much more readily than if no membrane 
intervened. Owing to the character of the articulations, when the handle 
of the malleus is drawn inward, the position of the bones is so changed that 
they form practically a solid rod, and are therefore much better adapted for the 
transmission of molecular vibrations than if the articulations remained loose. 
As the stapes bone is somewhat shorter than the malleus, its vibrations are 
smaller than those of the tympanic membrane, and by this arrangement the 
amplitude of the vibrations is diminished but their force increased. 

The Function of the Stapedius Muscle is, according to Henle, to 
fix the stapes bone so as to prevent too great a movement from being com¬ 
municated to it from the incus and transmitted to the perilymph. It may 
be looked upon therefore, as a protective muscle. 

The Function of the Eustachian tube is to maintain a free communi¬ 
cation between the cavity of the middle ear and naso-pharynx. The 
pressure of air within and without the ear is thus equalized, and the vibra¬ 
tions of the tympanic membrane permitted to attain their maximum; one 
of the conditions essential for the reception of sound waves. The impair¬ 
ment in the acuteness of hearing which is caused by an unequal pressure of 
the air in the middle ear can be shown: i. By closing the mouth and nose 
and forcing air from the lungs through the Eustachian tube into the ear, 
producing an increase in pressure. 2, By closing the nose and mouth, and 


THE SENSE OF HEARING. 


171 


making efforts at deglutition, which withdraws the air from the ear and 
diminishes its pressure. In both instances the free vibrations of the 
tympanic membrane are interfered with. The pharyngeal orifice of the 
Eustachian tube is opened by the action of certain of the muscles of 
deglutition, viz : the levator palati, tensor palati, and the palato-pharyngei 
muscles. 

The Internal Ear, or Labyrinth, is located in the petrous portion of 
the temporal bone, and consists of an osseous and membranous portion. 

The Osseous Labyrinth is divisible into three parts, viz: the vesti¬ 
bule, the semicircular canals and the cochlea. 

The vestibule .is a small, triangular cavity, which communicates with the 
middle ear by the foramen ovale; in the natural condition it is closed by 
the base of the stapes bone. The filaments of the auditory nerve enter the 
vestibule through small foramina in the inner wall, at the fovea hemi- 
spherica. 

The Semicircular canals are.three in number ; the superior vertical, the 
inferior vertical and the horizontal, each of which opens into the cavity of 
the vestibule by two openings, with the exception of the two vertical, which 
at one extremity open by a common orifice. 

The Cochlea forms the anterior part of the internal ear. It is a gradually 
tapering canal, about one and a half inches in length, which winds spirally 
around a central axis, the modiolus , two and a half times. The interior of 
the cochlea is partly divided into two passages by a thin plate of bone, the 
lamina osseous spiralis , which projects from the central axis two-thirds 
across the canal. These passages are termed the scala vestibuli and the 
scala tympani , from their communication with the vestibule and tympanum. 
The scala tympani communicates with the middle ear through the foramen 
rotundum , which, in the natural condition, is closed by the second mem- 
brana tympani; superiorly they are united by an opening, the helicotrema. 

The whole anterior of the labyrinth, the vestibule, the semicircular 
canals, and the scala of the cochlea, contains a clear, limpid fluid, the peri¬ 
lymph, secreted by the periosteum lining the osseous walls. 

The Membranous Labyrinth corresponds to the osseous labyrinth 
with respect to form, though somewhat smaller in size. 

The Vestibular portion consists of two small sacs, the utricle and saccule. 

The Semicircular canals communicate with the utricle in the same 
manner as the bony canals communicate with the vestibule. The saccule 
communicates with the membranous cochlea by the canalis reuniens. In 
the interior of the utricle and saccule, at the entrance of the auditory nerve, 


172 


HUMAN PHYSIOLOGY. 


are small masses of carbonate of lime crystals, constituting the otoliths. 
Their function is unknown. 

The Membranous cochlea is a closed tube, commencing by a blind 
extremity at the first turn of the cochlea, and terminating at its apex by a 
blind extremity also. It is situated between the edge of the osseous lamina 
spiralis and the outer wall of the bony cochlea, and follows it in its turns 
around the modiolus. 

A transverse section of the cochlea shows that it is divided into two 
portions by the osseous lamina and the basilar membrane: I. The scala 
vestibuli, bounded by the periosteum and membrane of Reissner. 2. The 
scala tympani , occupying the inferior portion, and bounded above by the 
septum, composed of the osseous lamina and the membrana basilaris. 

The true membranous canal is situated between the membrane of Reiss¬ 
ner and the basilar membrane. It is triangular in shape, but is partly 
divided into a triangular portion and a quadrilateral portion by the tectorial 
membrane. 

The Organ of Corti is situated in the quadrilateral portion of the canal, 
and consists of pillars of rods, of the consistence of cartilage. They are 
arranged in two rows; the one internal, the other external; these rods rest 
upon the basilar membrane; their bases are separated from each other, but 
their upper extremities are united, forming an arcade. In the internal row 
it is estimated there are about 3500, and in the external row about 5200 of 
these rods. 

On the inner side of the internal row is a single layer of elongated hair 
cells; on the outer surface of the external row are three such layers of hair 
cells. Nothing definite is known as to their function. 

The Endolymph occupies the interior of the utricle, saccule, membranous 
canals, and bathes the strictures in the interior of the membranous cochlea, 
throughout its entire extent. 

The Auditory Nerve at the bottom of the internal auditory meatus 
divides into (1) a vestibular branch, which is distributed to the utricle and 
semicircular canals; (2) a cochlear branch, which passes into the central 
axis at its base, and ascends to its apex; as it ascends, fibres are given off, 
which pass between the plates of the osseous lamina, to be ultimately con¬ 
nected with the organ of Corti. 

The Function of the semicircular canals appears to be to assist in main¬ 
taining the equilibrium of the body; destruction of the vertical canal is 
followed by an oscillation of the head upward and downward ; destruction 
of the horizontal canal is followed by oscillations from left to right. When 


VOICE AND SPEECH. 


173 


the canals are injured on both sides, the animal loses the power of main¬ 
taining equilibrium upon making muscular movements. 

Function of tke Cochlea. It is regarded as possessing the power ot 
appreciating the quality of pitch and the shades of different musical tones. 
The elements of the organ of Corti are analogous, in some respects, to a 
musical instrument, and are supposed, by Helmholtz, to be tuned so as to 
vibrate in unison with the different tones conveyed to the internal ear. 

Summary. The waves of sound are gathered together by the pinna 
and external auditory meatus, and conveyed to the membrana tympani. 
This membrane, made tense or lax by the action of the tensor tympani 
and laxator tympani muscles, is enabled to receive sound waves of either 
a high or low pitch. The vibrations are conducted across the middle ear 
by a chain of bones to the foramen ovale, and by the column of air of 
the tympanum to the foramen rotundum, which is closed by the second 
membrana tympani; the pressure of the air in the tympanum being regu¬ 
lated by the Eustachian tube. 

The internal ear finally receives the vibrations, which excite vibrations 
successively in the perilymph, the walls of the membranous labyrinth, the 
endolymph, and, lastly, the terminal filaments of the auditory nerve, by 
which they are conveyed to the brain. 


VOICE AND SPEECH. 

The Larynx is the organ of voice. Speech is a modification of voice, 
and is produced by the teeth and the muscles of the lips and tongue, co¬ 
ordinated in their action by stimuli derived from the cerebrum. 

The Structures entering into the formation of the larynx are mainly 
the thyroid , cricoid and arytenoid cartilages; they are so situated and 
united by means of ligaments and muscles as to form a firm cartilaginous 
box. The larynx is covered externally by fibrous tissue, and lined inter¬ 
nally with mucous membrane. 

The Vocal Cords are four ligamentous bands, running antero-posteri- 
orly across the upper portion of the larynx, and are divided into the two 
superior or false vocal cords, and the two inferior or true vocal cords; 
they are attached anteriorly to the receding angle of the thyroid cartilages 
and posteriorly to the anterior part of the base of the arytenoid cartilages. 
The space between the true vocal cords is the rima glottidis. 

The Muscles which have a direct action upon the movements of the 


174 


HUMAN PHYSIOLOGY. 


vocal cords are nine in number, and take their names from their points of 
origin and insertion, viz: the two crico-thyroid, two thyro-arytenoid , two 
posterior crico-arytenoid, two lateral crico-arytenoid, and one arytenoid 
muscles. 

The crico-thyroid muscles, by their contraction, render the vocal cords 
more tense by drawing down the anterior portion of the thyroid cartilage 
and approximating it to the cricoid, and at the same time tilting the pos¬ 
terior portion of the cricoid and arytenoid cartilages backward. 

The thyro-arytenoid, by their contraction, relax the vocal cords by draw¬ 
ing the arytenoid cartilage forward and the thyroid backward. 

The posterior crico-arytenoid muscles, by their contraction, rotate the 
arytenoid cartilages outward and thus separate the vocal cords and enlarge 
the aperture of the glottis. They principally aid the respiratory movements 
during inspiration. 

The lateral crico-arytenoid muscles are antagonistic to the former, and 
by their contraction rotate the arytenoid cartilages so as to approximate the 
vocal cords and constrict the glottis. 

The arytenoid muscle assists in the closure of the aperture of the glottis. 

The inferior laryngeal nerve animates all the muscles of the larynx, with 
the exception of the crico thyroid. 

Movements of the Vocal Cords. During respiration the move¬ 
ments of the vocal cords differ from those occurring during the production 
of voice. 

At each inspiration, the true vocal cords are widely separated, and the 
aperture of the glottis is enlarged by the action of the crico-arytenoid 
muscles, which rotate outward the anterior angle of the base of the aryte¬ 
noid cartilages; at each expiration the larynx becomes passive; the 
elasticity of the vocal cords returns them to their original position, and the 
air is forced out by the elasticity of the lungs and the walls of the thorax. 

Phonation. As soon as phonation is about to be accomplished a marked 
change in the glottis is noticed with the aid of the laryngoscope. The 
true vocal cords suddenly become approximated and are made parallel, 
giving to the glottis the appearance of a narrow slit, the edges of which are 
capable of vibrating accurately and rapidly; at the same time their tension 
is much increased. 

With the vocal cords thus prepared, the expiratory muscles force the 
column of air into the lungs and trachea through the glottis, throwing the 
edges of the cords into vibration. 

The pitch of sounds depends upon the extent to which the vocal cords 
are made tense and the length of the aperture through which the air passes. 


VOICE AND SPEECH. 


175 


In the production of sounds of a high pitch the tension of the vocal cords 
becomes very marked, and the glottis diminished in length. When grave 
sounds, having a low pitch, are omitted from the larynx, the vocal cords 
are less tense and their vibrations are large and loose. 

The quality of voice depends upon the length, size and thickness of the 
cords, and the size, form and construction of the trachea, larynx and the 
resonant cavities of the pharynx, nose and mouth. 

The compass of the voice comprehends from two to three octaves. The 
range is different in the two sexes; the lowest note of the male being about 
one octave lower than the lowest note of the female : while the highest 
note of the male is an octave less than the highest note of the female. 

The varieties of voices, e. g ., bass, baritone, tenor, contralto, mezzo- 
soprano and soprano, are due to the length of the vocal cords; being 
longer when the voice has a low pitch, and shorter when it has a high pitch. 

Speech is the faculty of expressing ideas by means of combinations of 
sounds, in obedience to the dictates of the cerebrum. 

Articulate sounds may be divided into vowels and consonants. The 
vowel sounds , a, <?, i, o, u, are produced in the larynx by the vocal cords. 
The consonantal sounds are produced in the air passages above the larynx 
by an interruption of the current of air by the lips, tongue and teeth; the 
consonants may be divided into: (i) mutes, b , d, k,p, t , c, g; (2) dentals, 
d, j, s, t, z; (3 )nasals, m t n , ng; (4) labials, £,/,/, v, m; (5) gutturals, 
k , g, c, and g hard ; (6) liquids, /, m, n, r. 


17G 


HUMAN PHYSIOLOGY. 


REPRODUCTION. 


Reproduction is the function by which the species is preserved, and 
accomplished by the organs of generation in the two sexes. 


GENERATIVE ORGANS OF THE FEMALE. 

The Generative Organs of the Female consist of the ovaries, Fallo¬ 
pian tubes, uterus and vagina. 

The Ovaries are two small, ovoid, flattened bodies, measuring one inch 
and a half in length and three-quarters of an inch in width; they are situ¬ 
ated in the cavity of the pelvis, and imbedded in the posterior layer of the 
broad ligament; attached to the uterus by a round ligament, and to the ex¬ 
tremities of the Fallopian tubes by the fimbriae. The ovary consists of an 
external membrane of fibrous tissue, the cortical portion, in which are im¬ 
bedded the Graafian vesicles , and an internal portion, the stroma , contain¬ 
ing blood vessels. 

The Graafian Vesicles are exceedingly numerous, but situated only in 
the cortical portion. Although the ovary contains the vesicles from the 
period of birth, it is only at the period of puberty that they attain their full 
development. From this time onward to the catamenial period, there is a 
constant growth and maturation of the Graafian vesicles. They consist of 
an external investment, composed of fibrous tissue and blood vessels, in the 
interior of which is a layer of cells forming the membrana granulosa ; at 
its lower portion there is an accumulation of cells, the proligerous disc , in 
which the ovum is contained. The cavity of the vesicle contains a slightly 
yellowish, alkaline, albuminous fluid. 

The Ovum is a globular body, measuring about the of an inch in 
diameter; it consists of an external investing membrane, the vitelline mem¬ 
brane, , a central granular substance, the vitellus or yelk , a nucleus, the 
germinal vesicle , in the interior of which is imbedded the nucleolus, or 
germinal spot. 

The Fallopian Tubes are about four inches in length, and extend out¬ 
ward from the upper angles of the uterus, between the folds of the broad 
ligaments, and terminate in a fringed extremity, which is attached by one of 
the fringes to the ovary. They consist of three coats : (i) the external, or 


GENERATIVE ORGANS OF THE FEMALE. 


177 


peritoneal, (2) middle, or muscular, the fibres of which are arranged in a 
circular or longitudinal direction, (3) internal, or mucous, covered with 
ciliated epithelial cells, which are always waving from the ovary toward 
the uterus. 

The Uterus is pyriform in shape, and may be divided into a body and 
neck; it measures about three inches in length and two-inches in breadth 
in the unimpregnated state. At the lower extremity of the neck is the os 
externum; at the junction of the neck with the body is a constriction, the 
os internum. The cavity of the uterus is triangular in shape, the walls of 
which are almost in contact. 

The walls of the uterus are made up of several layers of non-striated 
muscular fibres, covered externally by peritoneum, and lined internally by 
mucous membrane, containing numerous tubular glands, and covered by 
ciliated epithelial cells. 

The Vagina is a membranous canal, from five to six inches in length, 
situated between the rectum and bladder. It extends obliquely upward 
from the surface, almost to the brim of the pelvis, and embraces at its upper 
extremity the neck of the uterus. 

Discharge of the Ovum. As the Graafian vesicle matures, it increases 
in size, from an augmentation of its liquid contents, and approaches the 
surface of the ovary, where it forms a projection, measuring from one-fourth 
to one-half an inch in size. The maturation of the vesicle occurs periodically, 
about every twenty-eight days, and is attended by the phenomena of men¬ 
struation. During this period of active congestion of the reproductive 
organs, the Graafian vesicle ruptures, the ovum and liquid contents escape, 
and are caught by the fimbriated extremity of the Fallopian tube, which 
has adapted itself to the posterior surface of the ovary. The passage of 
the ovum through the Fallopian tube into the uterus occupies from ten to 
fourteen days, and is accomplished by muscular contraction and the action 
of the ciliated epithelium. 

Menstruation is a periodical discharge of blood from the mucous mem¬ 
brane of the uterus, due to a fatty degeneration of the small blood vessels. 
Under the pressure of an increased amount of blood in the reproductive 
organs, attending the process of ovulation, the blood vessels rupture, and a 
hemorrhage takes place into the uterine cavity; thence it passes into the 
vagina. Menstruation lasts from five to six days, and the amount of blood 
discharged averages about five ounces. 

Corpus Luteum. For some time anterior to the rupture of a Graafian 
vesicle, it increases in size and becomes vascular; its walls become thick- 


178 


HUMAN PHYSIOLOGY. 


ened, from the deposition of a reddish-yellow, glutinous substance, a 
product of cell growth from the proper coat of the follicle and the membrana 
granulosa. After the ovum escapes, there is usually a small effusion of 
blood into the cavity of the follicle, which soon coagulates, loses its coloring 
matter, and acquires the characteristics of fibrin, but it takes no part in the 
formation of the corpus luteum. The walls of the follicle become convo¬ 
luted, vascular, and undergo hypertrophy, until they occupy the whole of 
the follicular cavity. At its period of fullest development, the corpus luteum 
measures three-fourths of an inch in length and half an inch in depth. In 
a few weeks the mass loses its red color, and becomes yeliow, constituting 
the corpus luteum ox yellow body. It then begins to retract, and becomes 
pale; and at the end of two months, nothing remains but a small cicatrix 
upon the surface of the ovary. Such are the changes in the follicle, if the 
ovum has not been impregnated. 

The corpus luteum, after impregnation has taken place, undergoes a 
much slower development, becomes larger, and continues during the entire 
period of gestation. The difference between the corpus luteum of the 
unimpregnated and pregnant condition is expressed in the following table 
by Dalton:— 


At the end of 
three weeks. 
One month. 


Two months. 


Four months. 


Six months. 


Nine months. 


Corpus Luteum of Menstruation. Corpus Luteum of Pregnancy. 


Three-quarters of an inch in 
reddish ; convoluted wall pale. 


diameter; central clot 


Smaller; convoluted 
wall bright yellow ; clot 
still reddish. 

Reduced to the condi¬ 
tion of an insignificant 
cicatrix. 

Absent or unnoticeable. 


Absent. 


Absent. 


Larger ; convoluted wall 
bright yellow; clot still red¬ 
dish. 

Seven-eighths of an inch 
in diameter; convoluted wall 
bright yellow; clot perfectly 
decolorized. 

Seven-eighths of an inch 
in diameter; clot pale and 
fibrinous; convoluted wall 
dull yellow. 

Still as large as at the end 
of second month; clot fibrin¬ 
ous ; convoluted wall paler. 

Half an inch in diameter; 
central clot converted into a 
radiating cicatrix ; external 
wall tolerably thick and con¬ 
voluted, but without any 
bright yellow color. 




GENERATIVE ORGANS OF THE MALE. 


179 


GENERATIVE ORGANS OF THE MALE. 

The Generative Organs of the Male consist of the testicles, vasa 
deferentia, vesiculce seminales and penis. 

The Testicles, the essential organs of reproduction in the male, are 
two oblong glands, about an inch and a half in length, compressed from 
side to side, and situated in the cavity of the scrotum. 

The proper coat of the testicle, the tunica albuginea , is a white, fibrous 
structure, about the of an inch in thickness; after enveloping the testicle, 
it is reflected into its interior at the posterior border, and forms a vertical 
process, the mediastinum testes , from which septa are given off, dividing 
the testicle in lobules. 

The substance of the testicle is made up of the seminiferous tubules , 
which exist to the number of 840; they are exceedingly convoluted, and 
when unraveled are about 30 inches in length. As they pass toward the 
apices of the lobules they become less convoluted, and terminate in from 
20 to 30 straight ducts, the vasa recta , which pass upward through the 
mediastinum and constitute the rete testis. At the upper part of the 
mediastinum the tubules unite to form from 9 to 30 small ducts, the vasa 
ejferentia , which become convoluted, and form the globus major of the 
epididymis; the continuation of the tubes downward behind the testicle 
and a second convolution constitutes the body and globus minor. 

The seminal tubule consists of a basement membrane lined by granular 
nucleated epithelium. 

The Vas Deferens, the excretory duct of the testicle, is about two feet 
in length, and may be traced upward from the epididymis to the under sur¬ 
face of the base of the bladder, where it unites with the duct of the vesicula 
seminalis, to form the ejaculatory duct. 

The Vesiculse Seminales are two lobulated, pyriform bodies, about 
two inches in length, situated on the under surface of the bladder. 

They have an external fibrous coat, a middle muscular coat, and an 
internal mucous coat, covered by epithelium, which secretes a mucous fluid. 
The vesiculoe seminales serve as reservoirs, in which the seminal fluid is 
temporarily stored up. 

The Ejaculatory Duct, about ^ of an inch in length, opens into the 
urethra, and is formed by the union of the vasa deferentia and the ducts of 
the vesiculae seminales. 

The Prostate Gland surrounds the posterior extremity of the urethra, 
and opens into it by from twenty to thirty openings, the orifices of the pros- 


180 


HUMAN PHYSIOLOGY. 


tatic tubules. The gland secretes a fluid which forms part of the semen, 
and assists in maintaining the vitality of the spermatozoa. 

Semen is a complex fluid, made up of the secretions from the testicles, 
the vesiculse seminales, the prostatic and urethral glands. It is grayish- 
white in color, mucilaginous in consistence, of a characteristic odor, and 
somewhat heavier than water. From half a drachm to a drachm is ejacu¬ 
lated at each orgasm. 

The Spermatozoa are peculiar anatomical elements, developed within 
the seminal tubules, and possess the power of spontaneous movement. 
The spermatozoa consist of a conoidal head and a long filamentous tail, 
which is in continuous and active motion; as long as they remain in the 
vas deferens they are quiescent, but when free to move in the fluid of the 
vesiculse seminales, become very active. 

Origin. The spermatozoa appear at the age of puberty, and are then 
constantly formed until an advanced age. They are developed from the 
nuclei of large, round cells contained in the anterior of the seminal tubules, 
as many as fifteen to twenty developing in a single cell. 

When the spermatozoa are introduced into the vagina, they pass readily 
into the uterus and through the Fallopian tubes toward the ovaries, where 
they remain and retain their vitality for a period of from 8 to io days. 

Fecundation is the union of the spermatozoa with the ovum during its 
passage toward the uterus, and usually takes place in the Fallopian tube, 
just outside of the womb. After floating around the ovum in an active man¬ 
ner, they penetrate the vitelline membrane, pass into the interior of the 
vitellus, where they lose their vitality, and along with the germinal vesicle 
entirely disappear. 


DEVELOPMENT OF ACCESSORY STRUCTURES. 

Segmentation of the Vitellus. After the disappearance of the 
spermatozoa and the germinal vesicle there remains a transparent, granular, 
albuminous substance, in the centre of which a new nucleus soon appears; 
this constitutes the parent cells , and is the first stage in the development of 
the new being. 

Following this, the vitellus undergoes segmentation; a constriction 
appears on the opposite side of the vitellus, which gradually deepens, 
until the yelk is divided into two segments, each of which has a distinct 
nucleus and nucleolus; these two segments undergo a further division into 
four, the four into eight, the eight into others, and so on, until the entire 


DEVELOPMENT OF ACCESSORY STRUCTURES. 


181 


vitellus is divided into a great number of cells, each of which contains a 
nucleus and nucleolus. 

The peripheral cells of this “ mulberry mass ” then arrange themselves 
so as to form a membrane, and as they are subjected to mutual pressure, 
assume a polyhedral shape, which gives to the membrane a mosaic appear¬ 
ance. The central part of the vitellus becomes filled with a clear fluid. 
A secondary membrane shortly appears within the first, and the two together 
constitute the external and internal blastodermic membranes. 

Germinal Area. At about this period there is an accumulation of 
cells at a certain spot upon the surface of the blastodermic membranes 
which marks the position of the future embryo. This spot, at first circular, 
soon becomes elongated, and forms the primitive trace , around which is a 
clear space, the area pellucida , which is itself surrounded by a darker region, 
the area opaca. 

The primitive trace soon disappears, and the area pellucida becomes 
guitar-shaped; a new groove, the medullary groove , is now formed, which 
develops from before backward, and becomes the neural canal. 

Blastodermic Membranes. The embryo, at this period, consists *of 
three layers, viz.: the external and internal blastodermic membranes, and a 
middle membrane formed by a genesis of cells from their internal surfaces. 
These layers are known as the epiblast, mesoblast and hypoblast. 

The Epiblast gives rise to the central nervous system, the epidermis of 
the skin and its appendages, and the primitive kidneys. 

The Mesoblast gives rise to the dermis, muscles, bones, nerves, blood 
vessels, sympathetic nervous system, connective tissue, the urinary and 
reproductive apparatus and the walls of the alimentary canal. 

The Hypoblast gives rise to the epithelial lining of the alimentary canal 
and its glandular appendages, the liver and pancreas, and the epithelium 
of the respiratory tract. 

Dorsal Laminae. As development advances, the true medullary 
groove deepens, and there arise two longitudinal elevations of the epiblast, 
the dorsal lamince , one on either side of the groove, which grow up, arch 
over and unite so as to form a closed tube, the primitive central nervous 
system. 

The Chorda Dorsalis is a cylindrical rod running almost throughout 
the entire length of the embryo. It is formed by an aggregation of meso- 
blastic cells, and situated immediately beneath the medullary groove. 

Primitive Vertebrae. On either side of the neural canal the cells 
of the mesoblast undergo a longitudinal thickening, which develops and 


182 


HUMAN PHYSIOLOGY. 


extends around the neural canal and the chorda dorsalis, and forms the 
arches and bodies of the vertebrae. They become divided transversely into 
four-sided segments. 

The Mesoblast now separates into two layers; the external, joining with 
the epiblast, forms the somaiopleure; the internal, joining with the hypo¬ 
blast, forms the Splanchnopleure; the space between them constituting the 
pleuro-pe 7 'itoneal cavity. 

Visceral Laminae. The walls of the pleuro-peritoneal cavity are 
formed by a downward prolongation of the somatopleure (the visceral 
lamina), which, as they extend around in front, pinch off a portion of the 
yelk sac (formed by the splanchnopleure), which becomes the primitive 
alimentary canal; the lower portion, remaining outside of the body cavity, 
forms the umbilical vesicle, which after a time disappears. 

Formation of Fcetal Membranes. The Amnion appears shortly 
after the embyro begins to develop, and is formed by folds of the epiblast 
and external layer of the mesoblast, rising up in front and behind, and on 
each side; these amniotic folds gradually extend over the back of the 
efhbryo to a certain point, where they coalesce, and enclose a cavity, the 
amniotic cavity. The membranous partition between the folds disappears, 
and the outer layer recedes and becomes blended with the vitelline mem¬ 
brane, constituting the chorion, the external covering of the embryo. 

The Allantois. As the amnion develops, there grows out from the 
posterior portion of the alimentary canal a pouch, or diverticulum, the 
allantois, which carries blood vessels derived from the intestinal circulation. 
As it gradually enlarges, it becomes more vascular, and inserts itself be- 
tween'the two layers of the amnion, coming into intimate contact with the 
external layer. Finally, from increased growth, it completely surrounds 
the embryo, and its edges become fused together. 

In the bird, the allantois is a respiratory organ, absorbing oxygen and 
exhaling carbonic acid; it also absorbs nutritious matter from the interior 
of the egg. 

Amniotic Fluid. The amnion, when first formed, is in close contact 
with the surface of the ovum; but it soon enlarges, and becomes filled 
with a clear, transparent fluid, containing albumin, glucose, fatty matters, 
urea and inorganic salts. It increases in amount up to the latter period of 
gestation, when it amounts to about two pints. In the space between the 
amnion and allantois is a gelatinous material, which is encroached upon, 
and finally disappears as the amnion and allantois come in contact, at about 
the fifth month. 


DEVELOPMENT OF ACCESSORY STRUCTURE?. 


183 


The Chorion, the external investment of the embryo, is formed by a 
fusion of the original vitelline membrane, the external layer of the amnion, 
and the allantois. The external surface now becomes covered with villous 
processes, which increase in number and size by the continual budding 
and growth of club-shaped processes from the main stem, and give to the 
chorion a shaggy appearance. They consist of a homogeneous granular 
matter, and are penetrated by branches of the blood vessels derived from 
the aorta. 

The presence of villous processes in the uterine cavity is proof positive 
of the previous existence of a foetus. They are characteristic of the 
chorion, and are found under no other circumstances. 

At about the end of the second month the villosities begin to atrophy 
and disappear from the surface of the chorion, with the exception of those 
situated at the points of entrance of the foetal blood vessels, which occupy 
about one-third of its surface, where they continue to grow longer, become 
more vascular, and ultimately assist in the formation of the placenta; the 
remaining two-thirds of the surface loses its villi and blood vessels, and 
becomes a simple membrane. 

The Umbilical Cord connects the foetus with that portion of the 
chorion which forms the foetal side of the placenta. It is a process of the 
allantois, and contains two arteries and a vein, which have a more or less 
spiral direction. It appears at the end of the first month, and gradually 
increases in length, until, at the end of gestation, it measures about twenty 
inches. The cord is also surrounded by a process of the amnion. 

Development of the Decidual Membrane. The interior of the 
uterus is lined by a thin, delicate mucous membrane, in which gre im 
bedded immense numbers of tubules, terminating in blind extremities, the 
uterine tubules. At each period of menstruation the mucous membrane 
becomes thickened and vascular, which condition, however, disappears 
after the usual menstrual discharge. When the ovum becomes fecundated, 
the mucous membrane takes on an increased growth, becomes more hyper¬ 
trophied and vascular, sends up little processes, or elevations from its sur¬ 
face, and constitutes the decidua vera. 

As the ovum passes from the Fallopian tube into the interior of the 
uterus, the primitive vitelline membrane, covered with villosities, becomes 
entangled with the processes of the mucous membrane. A portion of the 
decidua vera then grows up on all sides, and encloses the ovum, forming 
the decidua reflexa, while the villous processes of the chorion insert them¬ 
selves into the uterine tubules, and in the mucous membrane between 
them. 


184 


HUMAN PHYSIOLOGY. 


As development advances the decidua reflexa increases in size, and at 
about the end of the fourth month comes in contact with the decidua vera, 
with which it is ultimately fused. 

The Placenta. Of all the embryonic structures, the placenta is the 
most important. It is formed in the third month, and then increases in size 
until the seventh month, when a retrogressive metamorphosis takes place 
until its separation during labor, at which time it is of an oval or rounded 
shape, and measures from seven to nine inches in length, six to eight 
inches in breadth, and weighs from fifteen to twenty ounces. It is most 
frequently situated at the upper and posterior part of the inner surface of 
the uterus. 

The placenta consists of two portions, a foetal and a maternal. 

The Foetal portion is formed by the villi of the chorion, which, by devel¬ 
oping, rapidly increase in size and number. They become branched and 
penetrate the uterine tubules, which enlarge and receive their many ramifi¬ 
cations. The capillary blood vessels in the anterior of the villi also enlarge 
and freely anastomose with each other. 

The Maternal portion is formed from that part of the hypertrophied and 
vascular decidual membrane between the ovum and the uterus, the decidua 
serotina. As the placenta increases in size, the maternal blood vessels 
around the tubules become more and more numerous, and gradually fuse 
together, forming great lakes, which constitute sinuses in the walls of the 
uterus. 

As the latter period of gestation approaches, the villi extend deeper into 
the decidua, while the sinuses in the maternal portion become larger and 
extend further into the chorion. Finally, from excessive development of 
the blood vessels, the structures between them disappear, and as their walls 
come in contact, they fuse together, so that, ultimately, the maternal and 
foetal blood are only separated by a thin layer of a homogeneous substance. 
When fully formed, the placenta consists principally of blood vessels inter¬ 
lacing in every direction. The blood of the mother passes from the uterine 
vessels into the lakes surrounding the villi; the blood from the child flows 
from the umbilical arteries into the interior of the villi; but there is not at 
any time an intermingling of blood, the two being separated by a delicate 
membrane formed by a fusion of the walls of the blood vessels and the 
walls of the villi and uterine sinuses. 

The function of the placenta, besides nutrition, is that of a respiratory 
organ , permitting the oxygen of the maternal blood to pass by osmosis 
through the delicate placental membrane into the blood of the foetus; at 
the same time permitting the carbonic acid and other waste products, the 


DEVELOPMENT OF THE EMBRYO. 


185 


result of nutritive changes in the foetus, to pass into the maternal blood, and 
so to be carried to the various eliminating organs. 

Through the placenta also passes all the nutritious materials of the 
maternal blood which are essential for the development of the embryo. 

At about the middle of gestation there develops beneath the decidual 
membrane a new mucous membrane, destined to perform the functions of 
the old when it is extruded from the womb, along with the other embryonic 
structures, during parturition. 


DEVELOPMENT OF THE EMBRYO. 

Nervous System. The cerebro-spinal axis is formed within the me¬ 
dullary canal by the development of cells from its inner surfaces, which 
as they increase fill up the canal, and there remains only the central canal 
of the cord. The external surface gives rise to the dura mater and pia 
mater. The neural canal thus formed is a tubular membrane; it terminates 
posteriorly in an oval dilatation, and anteriorly in a bulbous extremity, 
which soon becomes partially contracted, and forms the anterior, middle 
and posterior cerebral vesicles, from which are ultimately developed the 
cerebrum, the corpora quadrigemina, and medulla oblongata, respectively. 

The anterior vesicle soon subdivides into two secondary vesicles, the 
larger of which becomes the hemispheres, the smaller, the optic thalami; 
the posterior vesicle also divides into two; the anterior becoming the cere¬ 
bellum, the posterior, the pons Varolii and medulla oblongata. 

About the seventh week the straight chain of cerebral vesicles becomes 
curved from behind forward and forms three prominent angles. As devel¬ 
opment advances, the relative size of the encephalic masses changes. The 
cerebrum developing more rapidly than the posterior portion of the brain, 
soon grows backward and arches over the optic thalami and the lubercula 
quadrigemina; the cerebellum overlaps the medulla oblongata. 

The surface of the cerebral hemispheres is at first smooth, but at about 
the fourth month begins to be marked by the future fissures and convolutions. 

The Eye is formed by a little bud projecting from the side of the 
anterior vesicle. It is at first hollow, but becomes lined with nervous 
matter, forming the optic nerve and retina ; the remainder of the cavity is 
occupied by the vitreous body. The anterior portion of the pouch becomes 
invaginated and receives the crystalline lens , which is a product of the 
epiblast, as is also the cornea. The iris appears as a circular membrane 
without a central aperture, about the seventh week; the eyelids are formed 
between the second and third months. 

M 


186 


HUMAN PHYSIOLOGY. 


The Internal Ear is developed from the auditory vesicle , budding from 
the third cerebral vesicle; the membranous vestibule appears first, and from 
it diverticula are given off, which become the semicircular canals and 
cochlea. 

The cavity of the tympanum, the Eustachian tube, and the external 
auditory canal are the remains of the first branchial cleft; the cavity of this 
cleft being subdivided into the tympanum and external auditory meatus by 
the membrana tympani. 

The Skeleton. The chorda dorsalis, the primitive part of the vertebral 
column, is a cartilaginous rod situated beneath the medullary groove. It is 
a temporary structure, and disappears as the true bony vertebrae develop. 
On either side are the quadrate masses of the mesoblast, the primitive ver¬ 
tebrae, which send processes upward and around the medullary groove, and 
downward and around the chorda dorsalis, forming in these situations the 
arches and bodies of the future vertebrae. 

More externally the outer layer of the mesoblast and epiblast arch down¬ 
ward and forward, forming the ventral laminae, in which develop the 
muscles and bones of the abdominal walls. 

The true craniumis an anterior development of the vertebral column, and 
consists of the occipital, parietal and frontal segments, which correspond to 
the three cerebral vesicles. The base of the cranium consists, at this period, 
of a cartilaginous rod on either side of the anterior extremity of the chorda 
dorsalis, in which three centres of ossification appear, the basi-occipital, the 
basi-sphenoidal, and the pre-sphenoidal. They ultimately develop into the 
basilar process of the occipital bone and the body of the sphenoid. 

The entire skeletonxs at first either membranous or cartilaginous. At the 
beginning of the second month centres of ossification appear in the jaws and 
clavicle; as development advances, the ossific points in all the future bones 
extend, until ossification is completed. 

The limbs develop from four little buds projecting from the sides of the 
embryo, which, as they increase in length, separate into the thigh, leg and 
foot, and the arm, forearm and hand; the extremities of the limbs undergo 
subdivision, to form the fingers and toes. 

Face and Visceral Arches. In the facial and cervical regions the 
visceral laminae send up three processes, the visceral arches , separated by 
clefts, the visceral clefts. 

The first , or the mandibular arches , unite in the median line to form the 
lower jaw, and superiorly form the malleus. A process jutting from its 
base grows forward, unites with the fronto-nasal process growing from 


DEVELOPMENT OF THE EMBRYO. 


187 


above, and forms the upper jaw. When the superior maxillary processes 
fail to unite, there results the cleft-palate deformity; if the integument also 
fails to unite, there results the hare-lip deformity. The space above the 
mandibular arch becomes the mouth. 

The second arch develops the incus and stapes bones, the styloid process 
and ligament, and the lesser cornu of the hyoid bone. The cleft between 
the first and second arches partially closes up, but there remains an opening 
at the side which becomes the Eustachian tube, tympanic cavity, and exter¬ 
nal auditory meatus. 

The third arch develops the body and greater cornu of the hyoid 
bone. 

Alimentary Canal and its Appendages. The alimentary canal is 
formed by a pinching off of the yelk sac by the visceral plates as they grow 
downward and forward. It consists of three distinct portions, the fore gut, 
the hind gut, and the central part, which communicates for some time with 
the yelk sac. It is at first a straight tube, closed at both extremities, lying 
just beneath the vertebral column. The canal gradually increases in 
length, and becomes more or less convoluted; at its anterior portion two 
pouches appear, which become the cardiac and pyloric extremities of the 
stomach. At about the seventh week the inferior extremity of the intestine 
is brought into communication with the exterior, by an opening, the anus. 
Anteriorly the mouth and pharynx are formed by an involution of epiblast, 
which deepens until it communicates with the fore gut. 

The Liver appears as a slight protrusion from the sides of the alimentary 
canal, about the end of the first month ; it grows very rapidly, attains a 
large size, and almost fills up the abdominal cavity. The hepatic cells are 
derived from the intestinal epithelium, the vessels and connective tissue 
from the mesoblast. 

The Pancreas is formed by the hypoblastic membrane. It originates in 
two small ducts budding from the duodenum, which divide and subdivide, 
and develop the glandular structure. 

• The Lungs are developed from the anterior part of the oesophagus. At 
first a small bud appears, which, as it lengthens, divides into two branches; 
secondary and tertiary processes are given off these, which form the bron¬ 
chial tubes and air cells. The lungs originally extended into the abdomi¬ 
nal cavity, but become confined to the thorax by the development of the 
diaphragm. 

The Bladder is formed by a dilatation of that portion of the allantois 
remaining within the abdominal cavity. It is at first pear-shaped, and 
communicates with the intestine, but later becomes separated, and opens 


188 


HUMAN PHYSIOLOGY. 


exteriorly by the urethra. It is attached to the abdominal walls by a 
rounded cord, the urachus, the remains of a portion of the allantois. 

Genito-urinary Apparatus. The Wolffian bodies appear about the 
thirteenth day, as long hollow tubes running along each side of the primi¬ 
tive vertebral column. They are temporary structures, and are sometimes 
called the primordial kidneys. The Wolffian bodies consist of tubules 
which run transversely and are lined with epithelium; internally they 
become invaginated to receive tufts of blood vessels; externally they open 
into a common excretory duct, the duct of the Woffian body, which unites 
with the duct of the opposite body, and empties into the intestinal canal 
at a point opposite the allantois. On the outer side of the Wolffian body 
there appears another duct, the duct of Muller, which also opens into the 
intestine. 

Behind the Wolffian bodies are developed the structures which become 
either the ovaries or testicles. In the development of the female, the 
Wolffian bodies and their ducts disappear; the extremities of the Mullerian 
ducts dilate and form the fimbriated extremity of the Fallopian tubes, while 
the lower portions coalesce to form the body of the uterus and vagina, 
which now separate themselves from the intestine. 

In the development of the male, the Mullerian ducts atrophy, and the 
ducts of the Wolffian body ultimately form the epididymis and vas deferens. 
About the seventh month the testicles begin to descend, and by the ninth 
month have passed through the abdominal ring into the scrotum. 

The Kidneys are developed out of the Wolffian bodies. They consist of 
little pyramidal lobules, composed of tubules which open at the apex into 
the pelvis. As they pass outward they become convoluted and cup-shaped 
at their extremities, receive a tuft of blood vessels, and form the Mal¬ 
pighian bodies. 

The ureters are developed from the kidneys, and pass downward to be 
connected with the bladder. 

The Circulatory Apparatus assumes three different forms at different 
periods of life, all having reference to the manner in which the embryo 
receives nutritious matter and is freed of waste products. 

The Vitelline circulation appears first and absorbs nutritious material 
from the vitellus. It is formed by blood vessels which emerge from the 
body and ramify over a portion of the vitelline membrane, constituting the 
area vasculosa. The heart, lying in the median line, gives off two arches 
which unite to form the abdominal aorta, from which two large arteries 
are given off, passing into the vascular area; the venous blood is returned 


DEVELOPMENT OF THE EMBRYO. 


189 


by veins which enter the heart. These vessels are known as the oriiphalo- 
mesenteric arteries and veins. The vitelline circulation is of short duration 
in the mammals, as the supply of nutritious matter in the vitellus soon 
becomes exhausted. 

The Placental circulation becomes established when the blood vessels 
in the allantois enter the villous processes of the chorion and come into 
close relationship with the maternal blood vessels. This circulation lasts 
during the whole of intra uterine life, but gives way at birth to the adult 
circulation, the change being made possible by the development of the 
circulatory apparatus. 

The Heart appears as a mass of cells coming off from the anterior por¬ 
tion of the intestine; its central part liquefies, and pulsations soon begin. 
The heart is at first tubular, receiving posteriorly the venous trunks and 
giving off anteriorly the arterial trunks. It soon becomes twisted upon 
itself, so that the two extremities lie upon the same plane. 

The heart now consists of a single auricle and a single ventricle. A 
septum growing from the apex of the ventricle divides it into two cavities, 
a right and a left. The auricles also become partly separated by a septum 
which is perforated by the foramen ovale. The arterial trunk becomes 
separated by a partition into two canals, which become, ultimately, the 
aorta and pulmonary artery. The auricles are separated from the ventricles 
by incomplete septa, through which the blood passes into the ventricles. 

Arteries. The aorta arises from the cephalic extremity of the heart and 
divides into two branches which ascend, one on each side of the intestine, 
and unite posteriorly to form the main aorta; posteriorly to these first aortic 
arches four others are developed, so that there are five altogether running 
along the visceral arches. The two anterior soon disappear. The third 
arch becomes the internal carotid and the external carotid; a part of the 
fourth arch , on the right side, becomes the subclavian artery, and the 
remainder atrophies and disappears, but on the left side it enlarges and 
becomes the permanent aorta; the fifth arch becomes the pulmonary artery 
on the left side. The communication between the pulmonary artery and 
the aorta, the ductus arteriosus , disappears at an early period. 

Veins. The venous system appears first as two short, transverse veins, 
the canals of Cuvier, formed by the union of the vertebral veins and the 
cardinal veins, which empty into the auricle. The inferior vena cava is 
formed as the kidneys develop, by the union of the renal veins, which, in a 
short time, receive branches from the lower extremities. The subclavian 
veins join the jugular as the upper extremities develop. The heart descends 
in the thorax, and the canals of Cuvier become oblique; they shortly 


190 


HUMAN PHYSIOLOGY. 


communicate by a transverse duct, which ultimately becomes the left 
innominate vein. The left canal of Cuvier atrophies and becomes a fibrous 
cord. A transverse branch now appears, which carries the blood from the 
left cardiac vein into the right, and becomes the vena azygos minor; the 
right cardinal vein becomes the vena azygos major. 

Circulation of Blood in the Foetus. The blood returning from the 
placenta, after having received oxygen, and being freed from carbonic 
acid, is carried by the umbilical vein to the under surface of the liver; here 
a portion of it passes through the ductus venosus into the ascending vena 
cava, while the remainder flows through the liver, and passes into the vena 
cava by the hepatic veins. When the blood is emptied into the right 
auricle, it is directed by the Eustachian valve, through the foramen ovale, 
into the left auricle, thence into the left ventricle, and so into the aorta to 
all parts of the system. The venous blood returning from the head and 
upper extremities is emptied, by the superior vena cava, into the right 
auricle, from which it passes into the right ventricle, and thence into the 
pulmonary artery. Owing to the condition of the lung, only a small por¬ 
tion flows through the pulmonary capillaries, the greater part passing 
through the ductus arteriosus, which opens into the aorta at a point below 
the origin of the carotid and subclavian arteries. The mixed blood now 
passes down the aorta, to supply the lower extremities, but a portion of 
it is directed, by the hypogastric arteries, to the placenta, to be again 
oxygenated. 

At birth, the placental circulation gives way to the circulation of the 
adult. As soon as the child begins to breathe, the lungs expand, blood 
flows freely through the pulmonary capillaries, and the ductus arteriosus 
begins to contract. The foramen ovale closes about the tenth day. The 
umbilical vein, the ductus venosus, and the hypogastric arteries become 
impervious in severai days, and ultimately form rounded cords. 


TABLE OF PHYSIOLOGICAL CONSTANTS. 


191 


TABLE OF PHYSIOLOGICAL CONSTANTS. 


Mean height of male, 5 feet 6inches; of female, 5 feet 2 inches. 

Mean weight of male, 145 pounds; of female, 121 pounds. 

Number of chemical elements in the human body; from 16 to 18. 
Number of proximate principles in the human body; about 100. 
Amount of water in the body weighing 145 pounds; 108 pounds. 

Amount of solids in the body weighing 145 pounds; 36 pounds. 

Amount of food required daily; 16 ounces meat, 10 ounces of bread, 3^ 
ounces of fat, 52 ounces of water. 

Amount of saliva secreted in 24 hours; about pounds. 

Function of saliva; converts starch into glucose. 

Active principle.of saliva ; ptyalin. 

Amount of gastric juice secreted in 24 hours; from 8 to 14 pounds. 
Functions of gastric juice; converts albumin into albuminose. 
Active principles of gastric juice ; pepsin and hydrochloric acid. 
Duration of digestion; from 3 to 5 hours. 

Amount of intestinal juice secreted in 24 hours; about 1 pound. 

Function of intestinal juice ; converts starch into glucose. 

Amount of pancreatic juice secreted in 24 hours; about pounds. 
Active principles of pancreatic juice; trypsin, amylopsin and 
steapsin. 

{ 1. Emulsifies fats. 

2. Converts albumin into albuminose. 

3. Converts starch into glucose. 

Amount of bile poured into the intestines daily; about 2pounds. 

1. Assists in the emulsification of fats. 

2. Stimulates the peristaltic movements. 

3. Prevents putrefactive changes in the food. 

4. Promotes the absorption of the fat. 

Amount of blood in the body; from 16 to 18 pounds. 

Size of red corpuscles ; of an inch. 

Size of white corpuscles ; of an inch. 

Shape of red corpuscles; circular biconcave disks. 

Shape of white corpuscles ; globular. 

Number of red corpuscles in a cubic millimetre of blood (the cubic ^ 
of an inch); 5,000,000, 


Functions: 


l 



192 


HUMAN PHYSIOLOGY. 


Function of red corpuscles ; to carry oxygen from the lungs to the tissues. 
Frequency of the heart’s pulsations per minute ; 72, on the average. 
Velocity of the blood movement in the arteries; about 16 inches per 
second. 

Length of time required for the blood to make an entire circuit of the 
vascular system; about 20 seconds. 

Amount of air passing in and out of the lungs at each respiratory act; 
from 20 to 30 cubic inches. 

Amount of air that can be taken into the lungs on a forced inspiration; 
110 cubic inches. 

Amount of reserve air in the lungs after an ordinary expiration; 100 cubic 
inches. 

Amount of residual air always remaining in the lungs; about 100 cubic 
inches. 

Vital capacity of the lungs ; 230 cubic inches. 

Entire volume of air passing in and out of the lungs in 24 hours; about 
400 cubic feet. 

Composition of the air; nitrogen, 79.19; oxygen, 20.81, per 100 parts. 
Amount of oxygen absorbed in 24 hours; 18 cubic feet. 

Amount of carbonic acid exhaled in 24 hours; 14 cubic feet. 
Temperature of the human body at the surface; 98^° F. 

Amount of urine excreted daily; from 40 to 50 ounces. 

Amount of urea excreted daily; 512 grains. 

Specific gravity of urine ; from 1.015 to 1.025. 

Number of spinal nerves; 31 pairs. 

Number of roots of origin; two; 1st, anterior, motor; 2d, posterior, 
sensory. 

Rate of transmission of nerve force ; about 100 feet per second. 

Number of cranial nerves ; 12 pairs. 

1. Olfactory, or 1st pair. 

2. Optic, or 2d pair. 

3. Auditory, or 8th pair. 

4. Chorda tympani for anterior % of tongue. 

5. Branches of glosso-pharyngeal, or 8th 
pair, for posterior of tongue. 

Motor nerves to eyeball and accessory structures ; motor oculi, or 3d 
pair; pathetic, or 4th pair; abducens, or 6th pair. 

Motor nerves to facial muscles; portio dura, facial, or 7th pair. 

Motor nerve to tongue ; hypoglossal or 12th pair. 

Motor nerve to laryngeal muscles ; spinal accessory or nth pair. 

Sensory nerve of the face ; trifacial or 5th pair. 


Nerve.s of special sense: 




TABLE OF PHYSIOLOGICAL CONSTANTS. 


193 


Sensory nerve of the pharynx; glosso-pharyngeal or 9th pair. 

Sensory nerves of the lungs, stomach, etc; pneumogastric or 10th 
pair. 

Length of spinal cord ; 16 to 18 inches, weight 1 y z ounces. 

Point of decussation of motor fibres ; at the medulla oblongata. 

Point of decussation of sensory fibres ; throughout the spinal cord. 

Function of antero-lateral columns of spinal cord; transmit motor 
impulses from the brain to the muscles. 

Functions of the posterior columns; assist in the coordination of mus ; 
cular movements. 

Functions of the medulla oblongata ; controls the functions of insaliva¬ 
tion, mastication, deglutition, respiration, circulation, etc. 

Functions of the corpora quadrigemina; physical centres for sight. 

Functions of the corpora striata ; centres for motion. 

Functions of the optic thalami; centres for sensation. 

Function of the cerebellum ; centre for the coordination of muscular 
movement. 

Function of the cerebrum ; centre for intelligence, reason and will. 

Centre for articulate language ; 3d frontal convolution on the left side of 
cerebrum. 

Number of coats to the eye ; three ; 1st, cornea and sclerotic; 2d, choroid; 
3d, retina. 

Function of iris ; regulates the amount of light entering the eye. 

Function of crystalline lens ; refracts the rays of light so as to form an 
image on the retina. 

Function of retina; receives the impressions of light. 

Function of membrana tympani; receives and transmits waves of sound 
to internal ear. 

Function of Eustachian tube ; regulates the passage of air into and from 
the middle ear. 

Function of semicircular canals ; assist in maintaining the equipoise of 
the body. 

Function of the cochlea; appreciates the shades and combinations of 
musical tones. 

Size of human ovum ; of an inch in diameter. 

Size of spermatozoa ; of an inch in length. 

Function of the placenta; acts as a respiratory and digestive organ for the 
foetus. 

Duration of pregnancy ; 280 days. 


TABLE SHOWING RELATION OF WEIGHTS AND 
MEASURES OF THE METRIC SYSTEM TO APPROX¬ 
IMATE WEIGHTS AND MEASURES OF THE U. S. 


MEASURES OF LENGTH. 
One Myriametre = 10,000 metres = 

One Kilometre = 1,000 “ = 

One Hectometre = ioo “ = 

One Decametre = io “ = 

{ the ten millionth part of a 
quarter of the Meridian of 
the Earth 

the tenth part of one metre = 

f the one hundredth part of \ _ 

\ one metre J 

j the one thousandth part of |_ 


One Decimetre 
One Centimetre = 

One Millimetre === 


One Myriagramme 
One Kilogramme 
One Hectogramme 
One Decagramme 

One Gramme 

One Decigramme 

One Centigramme 

One Milligramme 


One Myrialitre 
One Kilolitre 
One Hectolitre 

One Decalitre 

One Litre 

One Decilitre 

One Centilitre 

One Millilitre 


\ one metre. 

WEIGHTS. 
10,000 grammes 


32800. feet. 

3280. “ 

328.0 “ 

32 80 “ 

39.368 inches. 
3.936 
•393 (!) 

• 039 (^) 

26^ pounds Troy. 


-{ 


1,000 

IOO 

10 


= 2 2 / 


the weight of a cubic centi- \ _ 

metre of water at 4 0 C. J 
== the tenth part of a gramme = 

_ f the hundredth part of one \ _ 

\ gramme / 

_ f the thousandth part of one_ 

\ gramme J 

MEASURES OF CAPACITY. 

{ 10 cubic Metres or the T 
measure of 10 Milliers of v == 
water. j 

_ f 1 cubic Metre or the meas -1 _ 

\ ure of 1 Millier of water J 

{ 100 cubic Decimetres oM 
the measure of 1 Quintal V = 
of water J 

{ 10 cubic Decimetres or 
the measure of 1 Myria¬ 
gramme of water 

{ 1 cubic Decimetre or the') 
measure of 1 Kilogramme V 
of water J 

{ ioo cubic Centimetres or 
the measure of 1 Hecto¬ 
gramme of water 

{ 10 cubic Centimetres or 
the measure of one Deca¬ 
gramme of water 
1 cubic Centimetre or the') 
measure of 1 gramme of ( 
water J 


3^ ounces “ 

2]/ 2 drachms “ 

1 5-434 grains. 

1-543 (1#) “ 

•154 04 ) 

• OI 5 (&) 

2600. gallons. 

260. “ 

26. 

2.6 “ 

2.1 pints. 

3.3 ounces. 

2.7 drachms. 
16.2 minims. 



INDEX 


PAGE 


ABDUCENS NERVE .105 

Aberration, chromatic.163 

-spherical.163 

Absorption. 37 

-by the lacteals. 42 

-by the blood vessels. 42 

-of oxygen in respiration ... 65 

Accommodation of the eye.162 

Adipose tissue, uses of in the body . 13 

Adult circulation, establishment of at 

birth.190 

Air, atmospheric, composition of . . 65 

-amount exchanged in respira¬ 
tion . 64 

- changes in during respiration 66 

Albumin, uses of in the body .... 14 

Albuminoid substances. 14 

Alcohol, action of. 22 

Alimentary principles, classification of 21 

-albuminous principles .... 21 

-saccharine principles. 22 

-oleaginous principles. 22 

-inorganic principles. 22 

Alimentary canal, development of. . 187 

Allantois, development and function of 182 

Amnion, formation of.182 

Animal heat . . . . ■. 67 

Anterior columns of spinal cord . . . 117 

Area, germinal.181 

Arteries, properties of. 56 

Asphyxia .. . . 66 

Astigmatism.163 

Axis, cerebro-spinal.115 

-cylinder of nerves. 93 

OILE. 36 

Bladder, urinary. 79 

Blastodermic membranes.181 

Blood. 45 

-composition of plasma .... 45 

-coagulation of. 48 

-coloring matter of. 47 

-changes in, during respiration 66 

-circulation of. 51 

-rapidity of flow in arteries . . 57 

-rapidity of flow in capillaries . 58 

-pathological conditions of . . 50 

-corpuscles. 47 

-- origin of. 48 

-pressure. 56 

Burdach, column of.118 


PAGE 


PANALS OF CUVIER .... 189 

Capillary blood vessels. 57 

Capsule, internal.133 

-external.133 

Caudate nucleus.133 

Cells, structure of. . . .. 17 

-manifestations of life by ... 18 

-of anterior horns of gray matter 118 

Centre for articulate language . . . . 14=; 

Cerebrum.136 

-fissures and convolutions . . . 137 

-functions of.140 

-localization of functions . . . 143 

-motor area of.143 

-special centres of.144 

Cerebellum.134 

-forced movements of.135 

Cerebral vesicles of embryo.185 

Chemical composition of human body 10 

-elements, proximate quantity 

of in body. 17 

Chorda dorsalis.181 

-tympani nerve, course and func¬ 
tion of.ic8 

Chorion.183 

Chyle.43 

Ciliary muscle.162 

Circulation of blood. 51 

Claustrum.133 

Cochlea.171 

Columns of spinal cord.117 

Corium. 88 

Corpora Wolffiana.188 

-quadrigemina.132 

Corpus luteum. 177 

-striatum.133 

Corti, organ of. 172 

Cranial nerves.102 

Crura cerebri.131 

Crystalline lens.159 

•TNECIDUAL MEMBRANE . . 183 

Decussation of motor and sen¬ 
sory fibres.119 

Deglutition. 28 

-nervous circle of.129 

Development of accessory structures 

of embryo.180 

Digestion.24 

Ductus arteriosus.189 

-venosus.189 


195 














































































































IDG 


INDEX. 


PAGE 


T^AR.165 

■*“* Electrotonus.100 

Embryo, development of .185 

Endolymph.172 

Epidermis. 88 

Epididymis.179 

Epiglottis. 29 

Eustachian tube . 168 

Excretion. 76 

Eye.154 

-refracting apparatus of ... . 160 

-blind spot of.164 

RACIAL NERVE.108 

-paralysis, symptoms of . 109 

Fallopian tubes.176 

Faeces. 37 

Fat, uses of in the body. 14 

Female organs of generation .... 176 

Fissures and convolutions of brain . . 137 

Food. 19 

-percentage composition of . . 23 

-daily amount required .... 23 

-albuminous principles of. . . 21 

-saccharine principles of . . . 22 

-- oleaginous principles of . . 22 

-- inorganic principles of . . . 22 

Fovea centralis.164 


riALVANIC CURRENTS, EF- 

feet on nerves.101 

Ganglia.148 

-ophthalmic.148 

-Gasserian.148 

-spheno-palatine ..148 

-otic.148 

-sub-maxillary.148 

-semi-lunar.149 

Gases of the intestine. 37 

-condition of, in blood .... 66 

Gastric juice. 31 

-action of. 32 

Generation, male organs of.179 

-female organs of.176 

Globules of the blood. 47 

-of the lymph. 43 

Glomeruli of the kidneys. 77 

Glosso-pharyngeal nerve.no 

Glottis, respiratory movements of . . 63 

Glycogen. 86 

Glycogenic function of liver. 86 

Goll, column of.117 

Graafian follicles.176 

Gray matter of nervous system ... 93 


TUT AIR . 89 

Haemoglobin. 47 

Hearing, sense of.165 

Heart.•. 51 

-valves of. 51 

-sounds of. 53 

-influence of pneumogastric 

nerve upon .. 55 


TAGE 


Heart, ganglia of. 55 

-force exerted by left ventricle 54 

-work done by. 54 

-course of blood through ... 52 

-influence of nervous system 

upon. 55 

Hyaloid membrane.i54 

Hypermetropia.163 

Hypoglossal nerve.1x4 


TNCUS BONE .167 

Insalivation. 26 

-nervous circle of. 28 

Inspiration, movements of thorax in . 62 

Internal capsule.133 

-results of injury to.133 

Intestinal juice. 34 

Iris.156 

-action of.163 

Island of Reil.139 


I7IDNEYS ......... 

-excretion of urine by 


76 

80 


T ABYRINTH OF INTERNAL 

ear. 

-- function of cochlea. 

-function of semicircular canals 

Language, articulate, centre for . . . 

Larynx . 

Lateral columns of spinal cord . . . 
Laws of muscular contraction . . . 

Lens, crystalline. 

Lime phosphate. 

Liver . 

-secretion of bile by. 

-glycogenic function of ... . 

-elaboration of blood. 

-cells. 

Localization of functions in cerebrum 

Lungs.. 

-changes in blood while passing 

through . 

Lymph . . . 

Lymphatic glands. 

- vessels, origin and course of . 


171 

171 

170 

i45 

i73 

117 

101 

X59 

12 

83 

85 

86 

87 

84 

i43 

60 

66 

43 

39 

39 


TV/T AM MARY GLANDS .... 72 

■*■*'*■ Malleus bone.166 

Mastication. 25 

-nervous circle of. 25 

-muscles of. 25 

Medulla oblongata.127 

-- properties and functions of . . 126 

Membrana basilaris.172 

-tympani.166 

Menstruation.177 

Middle ear.166 

Milk. 73 

Motor centres of cerebrum.143 

Muscles, properties of. 98 

Myopia. 163 



































































































































INDEX. 


197 


PAGE 


■JVT ERVE, OLFACTORY .... 102 

' -optic.103 

-motor oculi.104 

-pathetic.105 


trigeminal.106 


-abducens.105 

- facial. 108 

-auditory.109 

-glosso-pharyngeal,.no 

-pneumogastric.m 

-spinal accessory . . . . . . , 113 

-hypoglossal.114 

-cells, structure of. 92 

-fibres, terminations of ... . 94 

-force, rate of transmission of . 98 

-roots, function of anterior and 

posterior.. . . 118 

Nerves, centrifugal and centripetal, 95, 96 

-cranial.102 

-decussation of motor and sen¬ 
sory .119 

-vaso-motor.129 

-properties and functions of . . 95 

-spinal.118 

Nervous system. 92 

-white and gray matter of. . . 93 

-cerebro-spinal. 92 

-sympathetic.147 

Nucleus caudatus.133 

-lenticularis.133 

QLFACTORY NERVES . ... 102 

Ophthalmic ganglion.148 

Optic nerves.103 

-thalamus.133 

-functions of. 134 

Organs of Corti.172 

Otic ganglion.148 

Ovaries’. ..176 

Ovum.176 

-discharge of from the ovary . 177 

Oxygen, absorption of by haemoglobin 47 

pACINIAN CORPUSCLES . . 95 

^ Pancreatic juice. 35 

Patheticus nerve.105 

Peptones. 3 2 

Perilymph.17 1 

Perspiration. 90 

Petrosal nerves, large and small. . . 108 

Phonation , ..174 

Physiology, definition of. 9 

Placenta, formation and function of . 181 

Pneumogastric nerve. hi 

Pons varolii.13 1 

Portal vein. 37 

Posterior columns of spinal cord . . 117 

-functions of.122 

Prehension. 25 

Presbyopia.163 

Pressure of blood in arteries. 56 


PAGE 


Proximate principles. 11 

-inorganic. n 

-organic, non-nitrogenized . . 12 

-organic, nitrogenized .... 14 

-of waste . .. 16 

-quantity of chemical elements 

in body .. 17 

Ptyalin. 27 

Pulse. 57 

Pyramidal tracts.119 

DED CORPUSCLES OF 

blood. 47 

Reflex movements of spinal cord . . 123 

-action, laws of.124 

Reproduction. 176 

Respiration. 59 

-movements of. 62 

-nervous mechanism of ... . 63 

-types of. 63 

-.-nervous circle of.130 

Retina.157 

OAL 1 VA. 27 

^ Sebaceous glands. 89 

Secretion. 69 

Semi-circular canals.171 

Semen.180 

Sight, sense of.154 

Skin. 88 

-relative sensibility of ... 151 

Smell, sense of.154 

Sounds of heart. 53 

Spermatozoa. 180 

Spheno-palatine ganglion.148 

Spinal accessory nerve.113 

Spinal cord.116 

-membranes of.116 

-structure of white matter . . . 117 

-structure of gray matter . . . 118 

-properties of.121 

-function of as a conductor . . 122 

-as an independent centre . . 122 

-decussation of motor and sen¬ 
sory fibres.119 

-reflex action of.123 

• special centres of *..125 

-paralysis, from injuries of . . 126 

-nerves, origin of.119 

-course of anterior and posterior 

roots of.119 

Spleen. 74 

Starvation, phenomena of. 20 

Stomach. 29 

Structural composition of the bod)' . 17 

Submaxillary ganglion.148 

Sugar, uses of in the body. 13 

Supra-renal capsules. 75 

Sudoriparous glands. 90 

Sympathetic nervous system .... 147 
-properties and functions of . . 149 













































































































































198 


INDEX. 


PAGE 

npASTE, SENSE OF .152 

-nerve of.153 

Teeth.25 

Tensor tympani muscle.170 

Testicles.179 

Thoracic duct. 41 

Thorax, enlargement of in inspiration 62 

Tissues, classification of. 18 

Tongue ... . ..152 

-motor nerve of ..153 

-sensory nerve of.153 

Touch, sense of.151 

Tiirck, column of . . .. .119 

U MBILICAL CORD .183 

Urea. 81 

Uric acid. 82 

Urine. 80 

-composition of. 80 

-average quantity of constitu¬ 
ents secreted daily. 81 


PAGE 


Urination, nervous mechanism of . . 79 

Uterus.117 

VAPOR, WATERY, OF 

v breath. 66 

Vascular glands. 74 

-system, development of . . 188 

Vaso-motor nerves, origin of . . . . 129 

Veins. 58 

Vesiculse seminales.179 

Vision, physical centre for.132 

-psychical centre for.146 

Vital capacity of lungs. 64 

Vocal cords.174 

Voice.173 

water, AMOUNT OF IN 
vv body. 12 

Wolffian bodies.188 








































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OF TITLE PAGE. / 


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Medical Dictionary: 


INCLUDING ALL THE WORDS AND PHRASES GENERALLY 
USED IN MEDICINE, WITH THEIR PROPER PRO' 
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BASED ON RECENT MEDICAL .LITERATURE. 


BY 


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OPHTHALMIC SURGEON TO THE PHILADELPHIA HOSPITAL AND CLINICAL CHIEF 
OPHTHALMOLOGICAL DEPARTMENT, GERMAN HOSPITAL, 
PHILADELPHIA. 


WITH ELABORATE TABLES OP THE BACILLI, MICROCOCCI, LEUCOMATNES, PTOMAINES, 
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WEIGHTS AND MEASURES, THERMOMETERS, ETC.; AND APPENDICES 
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CATALOGUE No. 7. 


JUNE, 1891. 


A CATALOGUE 

OF 

Books for Students. 

INCLUDING THE 

? QUIZ-COMPENDS ? 


CONTENTS. 


PAGE 

New Series of Manuals, 2,3,4,5 


Anatomy, . . . . 6 

Biology, . . . .11 

Chemistry, . . . . 6 

Children’s Diseases, . , 7 

Dentistry, . ... 8 
Dictionaries, . . .8 

Eye Diseases, . . .9 

Electricity, . ... 9 

Gynaecology, . . .10 

Hygiene, .... 9 
Materia Medica, . . .9 

Medical Jurisprudence, . 10 


Obstetrics. . 

Pathology, Histology, 
Pharmacy, . 

Physiology, . 

Practice of Medicine, 
Prescription Books, 
PQuiz-Compends ? . 14,15 
Skin Diseases, 

Surgery, . . . .13 

Therapeutics, . . .9 

Urine and Urinary Organs, 13 
Venereal Diseases, . .13 


PUBLISHED BY 

P. BLAKISTON, SON & CO., 

Medical Booksellers, Importers and Publishers. 

LARGE STOCK OF ALL STUDENTS’ BOOKS, AT 
THE LOWEST PRICES. 

1012 Walnut Street, Philadelphia. 

*** For sale by all Booksellers, or any book will be sent by mail, 
postpaid, upon receipt of price. Catalogues of books on all branches 
of Medicine, Dentistry, Pharmacy, etc., supplied upon application. 


4®= Gould's New Medical Dictionary Just Ready. See page ib. 













“An excellent Series of Manuals .”—Archives of Gyncecology. 

A NEW SERIES OF 

STUDENTS’ MANUALS 

On the various Branches of Medicine and Surgery. 

Can be used by Students of any College. 

Price of each, Handsome Cloth, $3.00. Full Leather, $3.50. 

The object of this series is to furnish good manuals 
for the medical student, that will strike the medium 
between the compend on one hand and the prolix text¬ 
book on the other—to contain all that is necessary for 
the student, without embarrassing him with a flood of 
theory and involved statements. They have been pre¬ 
pared by well-known men, who have had large experience 
as teachers and writers, and who are, therefore, well 
informed as to the needs of the student. 

Their mechanical execution is of the best—good type 
and paper, handsomely illustrated whenever illustrations 
are of use, and strongly bound in uniform style. 

Each book is sold separately at a remarkably low 
price, and the immediate success of several of the 
volumes shows that the series has met with popular 
favor. * 


No. 1. SURGERY. 236 Illustrations. 

A Manual of the Practice of Surgery. By Wm. J. 

Walsham, m.d., Asst. Surg. to, and Demonstrator of 

Surg. in, St. Bartholomew’s Hospital, London, etc. 

228 Illustrations. 

Presents the introductory facts in Surgery in clear, precise 
language, and contains all the latest advances in Pathology, 
Antiseptics, etc. 

“ It aims to occupy a position midway between the pretentious 
manual and the cumbersome System of Surgery, and its general 
character may be summed up in one word—practical .”—The Medi¬ 
cal Bulletin. 

“Walsham, besides being an excellent surgeon, is a teacher in 
its best sense, and having had very great experience in the 
preparation of candidates for examination, and their subsequent 
professional career, may be relied upon to have carried out his 
work successfully. Without following out in detail his arrange¬ 
ment, which is excellent, we can at once say that his book is an 
embodiment of modern ideas neatly strung together, with an amount 
of careful organization well suited to the candidate, and, indeed, to 
the practitioner .”—British Medical Journal. 

Price of eaoh Book, Cloth, $3.00; Leather, $3.50. 


THE NEW SERIES OF MANUALS. 


3 


No. 2. DISEASES OF WOMEN. 150 Illus. 

NEW EDITION. 

The Diseases of Women. Including Diseases of the 
Bladder and Urethra. By Dr. F. Winckel, Professor 
of Gynaecology and Director of the Royal University 
Clinic for Women, in Munich. Second Edition. Re¬ 
vised and Edited by Theophilus Parvin, M.D., 
Professor of Obstetrics and Diseases of Women and 
Children in Jefferson Medical College. 150 Engrav¬ 
ings, most of which are original. 

" The book will be a valuable one to physicians, and a safe and 
satisfactory one to put into the hands of students. It is issued in a 
neat and attractive form, and at a very reasonable price.”— Boston 
Medical and Surgical Journal. 

No. 3. OBSTETRICS. 227 Illustrations. 

A Manual of Midwifery. By Alfred Lewis Galabin, 
m.a., M.D., Obstetric Physician and Lecturer on Mid¬ 
wifery and the Diseases of Women at Guy’s Hospital, 
London; Examiner in Midwifery to the Conjoint 
Examining Board of England, etc. With 227 I 13 us. 

“ This manual is one we can strongly recommend to all who 
desire to study the science as well as the practice of midwifery. 
Students at the present time not only are expected to know the 
principles of diagnosis, and the treatment of the various emergen¬ 
cies and complications that occur in the practice of midwifery, but 
find that the tendency is for examiners to ask more questions 
relating to the science of the subject than was the custom a few 
years ago. * * * The general standard of the manual is high; 
and wherever the science and practice of midwifery are well taught 
it will be regarded as one of the most important text-books on the 
subject.”— London Practitioner. 

No. 4. PHYSIOLOGY. Fifth Edition. 

321 ILLUSTRATIONS AND A GLOSSARY. 

A Manual of Physiology. By Gerald F. Yeo, m.d., 
F.r.cs., Professor of Physiology in King’s College, 
London. 321 Illustrations and a Glossary of Terms. 
Fifth American from last English Edition, revised and 
improved. 758 pages. 

This volume was specially prepared to furnish students with a 
new text-book of Physiology, elementary so far as to avoid theories 
which have not borne the test of time and such details of methods 
as are unnecessary for students in our medical colleges. 

“The brief examination I have given it was so favorable that I 
placed it in the list of text-books recommended in the circular of the 
University Medical College.”— Prof\ Lewis A. Stimson, m.d., 
3j East 33d Street, New York. 

Price of each Book, Cloth, $ 3 . 00 ; Leather, $ 3 . 50 . 



4 


THE NEW SERIES OF MANUALS. 


No. 5. DISEASES OF CHILDREN. 

SECOND EDITION. 

A Manual. By J. F. Goodhart, m.d., Phys. to the 
Evelina Hospital for Children; Asst. Phys. to 
Guy’s Hospital, London. Second American Edition. 
Edited and Rearranged by Louis Starr, m.d., Clinical 
Prof, of Dis. of Children in the Hospital of the Univ. 
of Pennsylvania, and Physician to the Children’s Hos¬ 
pital, Phila. Containing many new Prescriptions, a list 
of over 50 Formulae, conforming to the U. S. Pharma¬ 
copoeia, and Directions for making Artificial Human 
Milk, for the Artificial Digestion of Milk, etc. Illus. 


“ The merits of the book are many. Aside from the praiseworthy 
work of the printer and binder, which gives us a print and page 
that delights the eye, there is the added charm of a style of writ¬ 
ing that is not wearisome, that makes its statements clearly and 
forcibly, and that knows when to stop when it has said enough. 
The insertion of typical temperature charts certainly enhances the 
value of the book. It is rare, too, to find in any text-book so many 
topics treated of. All the rarer and out-of-the-way diseases are 
given consideration. This we commend. It makes the work 
valuable .”—Archives of Pedriatics , July , i 8 qo. 

“ The author has avoided the not uncommon error of writing a 
book on general medicine and labeling it ‘ Diseases of Children,’ 
but has steadily kept in view the diseases which seemed to be 
incidental to childhood, or such points in disease as appear to be so 
peculiar to or pronounced in children as to justify insistence upon 
them. * * * A safe and reliable guide, and in many ways 
admirably adapted to the wants of the student and practitioner.”— 
American Journal of Medical Science. 

“ Thoroughly individual, original and earnest, the work evi¬ 
dently of a close observer and an independent thinker, this book, 
though small, as a handbook or compendium is by no means made 
up of bare outlines or standard facts .”—The Therapeutic Ga¬ 
zette. 

“ As it is said of some men, so it might be said of some books, 
that they are ‘bom to greatness.’ This new volume has, we 
believe, a mission, particularly in the hands of the younger 
members-of the profession. In these days of prolixity in medical 
literature, it is refreshing to meet with an author who knows both 
what to say and when he has said it. The work of Dr. Goodhart 
(admirably conformed, by Dr. Starr, to meet American require¬ 
ments) is the nearest approach to clinical teaching without the 
actual presence of clinical material that we have yet seen .”—New 
York Medical Record. 


Price of each Book, Cloth, $3.00 : Leather, $3.50. 



THE NEW SERIES OF MANUALS. 


5 


No. 6. PRACTICAL THERAPEUTICS. 

FOURTH EDITION, WITH AN INDEX OF DISEASES. 

Practical Therapeutics, considered with reference to 
Articles of the Materia Medica. Containing, also, an 
Index of Diseases, with a list of the Medicines 
applicable as Remedies. By Edward John Waring, 
m.d., f.r.c.p. Fourth Edition. Rewritten and Re¬ 
vised by Dudley W. Buxton, m.d., Asst, to the Prof, 
of Medicine at University College Hospital. 

“ We wish a copy could be put in the hands of every Student or 
Practitioner in the country. In our estimation, it is the best book 
of the kind ever written.”— N. Y. Medical Journal. 

“ Dr. Waring's Therapeutics has long been known as one of the 
most thorough and valuable of medical works. The amount of 
actual intellectual labor it represents is immense. . . . An in¬ 

dex of diseases, with the remedies appropriate for their treatment, 
closes the volume.”— Boston Medical and Surgical Reporter. 

“ The plan of this work is an admirable one, and one well calcu¬ 
lated to meet the wants of busy practitioners. There is a remark¬ 
able amount of information, accompanied with judicious comments, 
imparted in a concise yet agreeable style.”— Medical Record. 

No. 7. MEDICAL JURISPRUDENCE AND 
TOXICOLOGY. 

THIRD REVISED EDITION. 

By John J. Reese, m.d., Professor of Medical Jurispru¬ 
dence and Toxicology in the University of Pennsyl¬ 
vania ; President of the Medical Jurisprudence Society 
of Phila.; Third Edition, Revised and Enlarged. 

“ This admirable text-book.”— Amer.Jour. of Med. Sciences. 

“ We lay this volume aside, after a careful perusal of its pages, 
with the profound impression that it should be in the hands of every 

doctor and lawyer. It fully meets the wants of all students. 

He has succeeded in admirably condensing into a handy volume all 
the essential points.”— Cincinnati Lancet and Clinic. 

“ The book before us will, we think, be found to answer the ex¬ 
pectations of the student or practitioner seeking a manual of juris¬ 
prudence, and the call for a second edition is a flattering testimony 
to the value of the author’s present effort. The medical portion 
of this volume seems to be uniformly excellent, leaving little for 
adverse criticism. The information on the subject matter treated 
has been carefully compiled, in accordance with recent knowledge. 
The toxicological portion appears specially excellent. Of that por¬ 
tion of the work treating of the legal relations of the practitioner 
and medical witness, we can express a generally favorable ver¬ 
dict.”— Physician and Surgeon, Ann Arbor , Mich. 

Price of each Book, Cloth, $3,00; Leather, $3.50. 




6 


STUDENTS’ TEXT-BOOKS AND MANUALS. 


ANATOMY. 

Macalister’s Human Anatomy. 816 Illustrations. A new 

Text-book for Students and Practitioners, Systematic and Topo¬ 
graphical, including the Embryology, Histology and Morphology 
of Man. With special reference to the requirements of 
Practical Surgery and Medicine. With 816 Illustrations, 
400 of which are original. Octavo. Cloth, 7.50; Leather, 8.50 
Ballou’s Veterinary Anatomy and Physiology. Illustrated. 
By Wm. R. Ballou, m.d., Professor of Equine Anatomy at New 
York College of Veterinary Surgeons. 29 graphic Illustrations. 
i2mo. Cloth, 1.00; Interleaved for notes, 1.25 

Holden’s Anatomy. A manual of Dissection of the Human 
Body. Fifth Edition. Enlarged, with Marginal References and 
over 200 Illustrations. Octavo. 

Bound in Oilcloth, for the Dissecting Room, $4.50. 

** No student of Anatomy can take up this book without being 
pleased and instructed. Its Diagrams are original, striking and 
suggestive, giving more at a glance than pages of text description. 
* * * The text matches the illustrations in directness of prac¬ 
tical application and clearness of detail .”—New York Medical 
Record. 

Holden’s Human Osteology. Comprising a Description of the 
Bones, with Colored Delineations of the Attachments of the 
Muscles. The General and Microscopical Structure of Bone and 
its Development. With Lithographic Plates and Numerous Illus¬ 
trations. Seventh Edition. 8vo. Cloth, 6.00 

Holden’s Landmarks, Medical and Surgical. 4th ed. Clo., 1.25 
Heath’s Practical Anatomy. Sixth London Edition. 24 Col¬ 
ored Plates, and nearly 300 other Illustrations. Cloth, 5.00 

Potter’s Compend of Anatomy. Fifth Edition. Enlarged. 
16 Lithographic Plates. 117 Illustrations. 

Cloth, 1.00; Interleaved for Notes, 1.25 

CHEMISTRY. 

Bartley’s Medical Chemistry. Second Edition. A text-book 
prepared specially for Medical, Pharmaceutical and Dental Stu¬ 
dents. With 50 Illustrations, Plate of Absorption Spectra and 
Glossary of Chemical Terms. Revised and Enlarged. Cloth, 2.50 
Trimble. Practical and Analytical Chemistry. A Course in 
Chemical Analysis, by Henry Trimble, Prof, of Analytical Chem¬ 
istry in the Phila. College of Pharmacy. Illustrated. Third 
Edition. 8vo. Cloth, 1.50 

4 ®** See pages 2 to j for list 0/Students' Manuals. 




STUDENTS’ TEXT-BOOKS AND MANUALS. 


7 


Chemistry : — Continued. 

Bloxam’s Chemistry, Inorganic and Organic, with Experiments. 
Seventh Edition. Enlarged and Rewritten. 281 Illustrations. 

Cloth, 4.50; Leather, 5.50 
Richter’s Inorganic Chemistry. A text-book for Students. 
Third American, from Fifth German Edition. Translated by 
Prof. Edgar F. Smith, ph.d. 89 Wood Engravings and Colored 
Plate of Spectra. Cloth, 2.00 

Richter’s Organic Chemistry, or Chemistry of the Carbon 
Compounds. Illustrated. Second Edition. In Press. 

Symonds. Manual of Chemistry, for the special use of Medi¬ 
cal Students. By Brandreth Symonds, a.m., m.d., Asst. 
Physician Roosevelt Hospital, Out-Patient Department; Attend¬ 
ing Physician Northwestern Dispensary, New York. i2mo. 

Cloth, 2.00; Interleaved for Notes, 2.40 
Leffmann’s Compend of Chemistry. Inorganic and Organic. 
Including Urinary Analysis. Third Edition. Revised. 

Cloth, 1.00; Interleaved for Notes, 1.25 
Leffmann and Beam. Progressive Exercises in Practical 
Chemistry. i2mo. Illustrated. Cloth, 1.00 

Muter. Practical and Analytical Chemistry. Third Edi¬ 
tion. Revised and Illustrated. Nearly Ready. 

Holland. The Urine, Common Poisons, and Milk Analysis, 
Chemical and Microscopical. For Laboratory Use. Fourth 
Edition, Enlarged. Illustrated. Cloth, 1.00 

Van Niiys. Urine Analysis. Illus. Cloth, 2.00 

Wolff’s Applied Medical Chemistry. By Lawrence Wolff, 
m.d., Dem. of Chemistry in Jefferson Medical College. Clo., 1.00 

CHILDREN. 

Goodhart and Starr. The Diseases of Children. Second 
Edition. By J. F. Goodhart, m.d., Physician to the Evelina 
Hospital for Children; Assistant Physician to Guy’s Hospital, 
London. Revised and Edited by Louis Starr, m.d.. Clinical 
Professor of Diseases of Children in the Hospital of the Univer¬ 
sity of Pennsylvania; Physician to the Children’s Hospital, 
Philadelphia. Containing many Prescriptions and Formulae, 
conforming to the U. S. Pharmacopoeia, Directions for making 
Artificial Human Milk, for the Artificial Digestion of Milk, etc. 
Illustrated. Cloth, 3.00; Leather, 3.50 

Hatfield. Diseases of Children. By M. P. Hatfield, m.d., 
Professor of Diseases of Children, Chicago Medical College. 
Colored Plate. i2mo. Cloth, 1.00; Interleaved, 1.25 

4 ®=“ See pages 14 and 15 for list of ? Quiz- Contpends ? 




8 


STUDENTS’ TEXT-BOOKS AND MANUALS. 


Children :— Continued. 

Starr. Diseases of the Digestive Organs in Infancy and 
Childhood. With chapters on the Investigation of Disease, 
and on the General Management of Children. By Louis Starr, 
m.d.. Clinical Professor of Diseases of Children in the Univer¬ 
sity of Pennsylvania. Illus. Second Edition. Cloth, 2.25 

DENTISTRY. 

Fillebrown. Operative Dentistry. 330 Illus. Cloth, 2.50 
Flagg’s Plastics and Plastic Filling. 4th Ed. Cloth, 4.00 
Gorgas. Dental Medicine. A Manual of Materia Medica and 
Therapeutics. Third Edition. Cloth, 3.50 

Harris. Principles and Practice of Dentistry. Including 
Anatomy, Physiology, Pathology, Therapeutics, Dental Surgery 
and Mechanism. Twelfth Edition. Revised and enlarged by 
Professor Gorgas. 1028 Illustrations. Cloth, 7.00 ; Leather, 8.00 
Richardson’s Mechanical Dentistry. Fifth Edition. 569 
Illustrations. 8vo. Cloth, 4.50; Leather, 5.50 

Sewill. Dental Surgery. 200 Illustrations. 3d Ed. Clo., 3.00 
Taft’s Operative Dentistry. Dental Students and Practitioners. 

Fourth Edition. 100 Illustrations. Cloth, 4.25 ; Leather, 5.00 
Talbot. Irregularities of the Teeth, and their Treatment. 

Illustrated. 8vo. Second Edition. Cloth, 3.00 

Tomes’ Dental Anatomy. Third Ed. 191 Illus. Cloth, 4.00 

Tomes’ Dental Surgery. 3d Edition. Revised. 292 Illus. 

772 Pages. Cloth, 5.00 

Warren. Compend of Dental Pathology and Dental Medi¬ 
cine. Illustrated. Cloth, 1.00; Interleaved, 1.25 

DICTIONARIES. 

Gould’s New Medical Dictionary. Containing the Definition 
and Pronunciation of all words in Medicine, with many useful 
Tables etc. Dark Leather, 3.25; % Mor., Thumb Index 4.25 
Harris’ Dictionary of Dentistry. Fifth Edition. Completely 
revised and brought up to date by Prof. Gorgas. 

Cloth, 5.00 ; Leather, 6.00 
Cleaveland’s Pronouncing Pocket Medical Lexicon. 31st 
Edition. Giving correct Pronunciation and Definition. Very 
small pocket size. Cloth, red edges .75 ; pocket-book style, 1.00 
Longley’s Pocket Dictionary. The Student’s Medical Lexicon, 
giving Definition and Pronunciation of all Terms used in Medi¬ 
cine, with an Appendix giving Poisons and Their Antidotes, 
Abbreviations tfsed in Prescriptions, Metric Scale of Doses, etc. 
24mo. Cloth, 1.00; pocket-book style, 1.25 

4 ®=" See pages 2 to 5 for list 0/ Students' Manuals. 



STUDENTS’ TEXT-BOOKS AND MANUALS. 


9 


EYE. 

Hartridge on Refraction. 4th Ed. Cloth, 2.00 

Meyer. Diseases of the Eye. A complete Manual for Stu¬ 
dents and Physicians. 270 Illustrations and two Colored Plates. 
8vo. Cloth, 4.50; Leather, 5.50 

Swanzy. Diseases of the Eye and their Treatment. 158 
Illustrations. Third Edition. Cloth, 3 00 

Fox and Gould. Compend of Diseases of the Eye and 
Refraction. 2d Ed. Enlarged. 71 Illus. 39 Formulae. 

Cloth, 1.00 ; Interleaved for Notes, 1.25 

ELECTRICITY. 

Bigelow. Plain Talks on Medical Electricity and Batteries. 
Illustrated. Cloth, 1.00 

Mason’s Compend of Medical and Surgical Electricity. 
With numerous Illustrations. i2mo. Cloth, 1.00 

HYGIENE. 

Parkes’ (Ed. A.) Practical Hygiene. Seventh Edition, en¬ 
larged. Illustrated. 8vo. Cloth, 4.50 

Parkes’ (L. C.) Manual of Hygiene and Public Health. 

Second Edition, nmo. Cloth, 2.50 

Wilson’s Handbook of Hygiene and Sanitary Science. 

Seventh Edition. Revised and Illustrated. In Press. 

MATERIA MEDICA AND THERAPEUTICS. 
Potter’s Compend of Materia Medica, Therapeutics and 
Prescription Writing. Fifth Edition, revised and improved. 

Cloth, 1.00; Interleaved for Notes, 1.25 
Biddle’s Materia Medica. Eleventh Edition. By the late 
John B. Biddle, m.d., Professor of Materia Medica in Jefferson 
Medical College, Philadelphia. Revised, and rewritten, by 
Clement Biddle, m.d., Assist. Surgeon, U. S. N., assisted by 
Henry Morris, m.d. 8vo., illustrated. Cloth, 4.25; Leather, 5.00 

Potter. Materia Medica, Pharmacy and Therapeutics. 
Including Action of Medicines, Special Therapeutics, Pharma¬ 
cology, etc. Second Edition. Cloth, 4.00; Leather, 5.00 

Waring. Therapeutics. With an Index of Diseases and 
Remedies. 4th Edition. Revised. Cloth, 3.00; Leather, 3.50 
See pages 14 and ij for list 0/ f Quiz-Compends f 




10 STUDENTS’ TEXT-BOOKS AND MANUALS. 


MEDICAL JURISPRUDENCE. 

Reese. A Text-book of Medical Jurisprudence and Toxi¬ 
cology. By John J. Reese, m.d.. Professor of Medical Juris¬ 
prudence and Toxicology in the Medical Department of the 
University of Pennsylvania; President of the Medical Juris¬ 
prudence Society of Philadelphia; Physician to St. Joseph’s 
Hospital; Corresponding Member of The New York Medico¬ 
legal Society. Third Edition. Cloth, 3.00; Leather, 3.50 

OBSTETRICS AND GYNAECOLOGY. 

By ford. Diseases of Women. The Practice of Medicine and 
Surgery, as applied to the Diseases and Accidents Incident to 
Women. By W. H. Byford, a.m., m.d., Professor of Gynaecology 
in Rush Medical College and of Obstetrics in the Woman’s Med¬ 
ical College, etc., and Henry T. Byford, m.d., Surgeon to the 
Woman’s Hospital of Chicago ; Gynaecologist to St. Luke’s 
Hospital, etc. Fourth Edition. Revised, Rewritten and En¬ 
larged. With 306 Illustrations, over 100 of which are original. 
Octavo. 832 pages. Cloth, 5.00 ; Leather, 6.00 

Cazeaux and Tarnier’s Midwifery. With Appendix, by 

Munde. The Theory and Practice of Obstetrics ; including the 
Diseases of Pregnancy and Parturition, Obstetrical Operations, 
etc. By P. Cazeaux. Remodeled and rearranged, with revi¬ 
sions and additions, by S. Tarnier, m.d.. Professor of Obstetrics 
and Diseases of Women and Children in the Faculty of Medicine 
of Paris. Eighth American, from the Eighth French and First 
Italian Edition. Edited by Robert J. Hess, m.d., Physician to 
the Northern Dispensary, Philadelphia, with an appendix by 
Paul F. Munde, m.d., Professor of Gynaecology at the N. Y. 
Polyclinic. Illustrated by Chromo-Lithographs, Lithographs, 
and other Full-page Plates, seven of which are beautifully colored, 
and numerous Wood Engravings. Students' Edition. One 
Vol., 8vo. Cloth, 5.00; Leather, 6.00 

Lewers' Diseases of Women. A Practical Text-Book. 139 
Illustrations. Second Edition. Cloth, 2.50 

Parvin’s Winckel’s Diseases of Women. Second Edition. 

Including a Section on Diseases of the Bladder and Urethra. 
150 Illus. Revised. Seepages. Cloth, 3.00; Leather, 3.50 

Morris. Compend of Gynaecology. Illustrated. Cloth, 1.00 

Winckel’s Obstetrics. A Text-book on Midwifery, includ¬ 
ing the Diseases of Childbed. By Dr. F. Winckel, Professor 
of Gynaecology, and Director of the Royal University Clinic for 
Women, in Munich. Authorized Translation, by J. Clifton 
Edgar, m.d., Lecturer on Obstetrics, University Medical Col¬ 
lege, New York, with nearly 200 handsome illustrations, the 
majority of which are original with this work. Octavo. 

Cloth, 6.00; Leather, 7.00 

Landis’ Compend of Obstetrics. Illustrated. 4th edition, 
enlarged. Cloth, 1.00; Interleaved for Notes, 1.25 

See pages 2 to 5 for list of New Manuals. 




STUDENTS' TEXT-BOOKS AND MANUALS. 


11 


Obstetrics and Gyncecology : — Continued. 

Galabin’s Midwifery. By A. Lewis Galabin, m.d., f.r.c.f. 

227 Illustrations. See page 3. Cloth, 3.00; Leather, 3.50 

Rigby’s Obstetric Memoranda. 4th Edition. Cloth, .50 

Swayne’s Obstetric Aphorisms. For the use of Students 
commencing Midwifery Practice. 8th Ed. i2mo. Cloth, 1.25 

PATHOLOGY. HISTOLOGY. BIOLOGY. 

Bowlby. Surgical Pathology and Morbid Anatomy, for 
Students. 135 Illustrations. i2mo. Cloth, 2.00 

Davis’ Elementary Biology. Illustrated. Cloth, 4.00 

Gilliam’s Essentials of Pathology. A Handbook for Students. 
47 Illustrations. i2mo. Cloth, 2.00 

***The object of this book is to unfold to the beginner the funda¬ 
mentals of pathology in a plain, practical way, and by bringing 
them within easy comprehension to increase his interest in the study 
of the subject. 

Gibbes’ Practical Histology and Pathology. Third Edition. 
Enlarged. i2mo. Cloth, 1.75 

Virchow’s Post-Mortem Examinations. 3d Ed. Cloth, 1.00 

PHYSIOLOGY. 

Yeo’s Physiology. Fifth Edition. The most Popular Stu¬ 
dents' Book. By Gerald F. Yeo, m.d., f.r.c.s.. Professor of 
Physiology in King's College, London. Small Octavo. 758 
pages. 321 carefully printed Illustrations. With a Full 
Glossary and Index. See Page3. Cloth, 3.00; Leather, 3.50 
Brubaker’s Compend of Physiology. Illustrated. Sixth 
Edition. Cloth, 1.00; Interleaved for Notes, 1.25 

Stirling. Practical Physiology, including Chemical and Ex¬ 
perimental Physiology. 142 Illustrations. Cloth, 2.25 

Kirke’s Physiology. New 12th Ed. Thoroughly Revised and 
Enlarged. 502 Illustrations. Cloth, 4.00; Leather, 5.00 

Landois’ Human Physiology. Including Histology and Micro¬ 
scopical Anatomy, and with special reference to Practical Medi¬ 
cine. Third Edition. Translated and Edited by Prof. Stirling. 
692 Illustrations. Cloth, 6.50; Leather, 7.50 

“ With this Text-book at his command, no student could fail in 
his examination.”— Lancet . 

Sanderson’s Physiological Laboratory. Being Practical Ex¬ 
ercises for the Student. 350 Illustrations. 8vo. Cloth, 5.00 

PRACTICE. 

Taylor. Practice of Medicine. A Manual. By Frederick 
Taylor, m.d., Physician to, and Lecturer on Medicine at, Guy's 
Hospital, London ; Physician to Evelina Hospital for Sick Chil¬ 
dren, and Examiner in Materia Medica and Pharmaceutical 
Chemistry, University of London. Cloth, 4.00; Leather, 5.00 

See pages 14 and 13 for list 0f ? Quiz- Compends f 



12 STUDENTS’ TEXT-BOOKS AND MANUALS. 


Practice :— Continued. 

Roberts’ Practice. New Revised Edition. A Handbook 
of the Theory and Practice of Medicine. By Frederick T. 
Roberts, m.d. ; m.r.c.p., Professor of Clinical Medicine and 
Therapeutics in University College Hospital, London. Seventh 
Edition. Octavo. Cloth, 5.50 ; Sheep, 6.50 

Hughes. Compend of the Practice of Medicine. 4th Edi¬ 
tion. Two parts, each, Cloth, 1.00; Interleaved for Notes, 1.25 
Part i.—C ontinued, Eruptive and Periodical Fevers, Diseases 
of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver, 
Kidneys, etc., and General Diseases, etc. 

Part ii.— Diseases of the Respiratory System, Circulatory 
System and Nervous System; Diseases of the Blood, etc. 

Physicians’ Edition. Fourth Edition. Including a Section 
on Skin Diseases. With Index. 1 vol. Full Morocco, Gilt, 2.50 
From John A. Robinson , M.D., Assistant to Chair of Clinical 
Medicine , now Lecturer on Materia Medica, Rush Medical Col¬ 
lege, Chicago. 

“ Meets with my hearty approbation as a substitute for the 
ordinary note books almost universally used by medical students. 
It is concise, accurate, well arranged and lucid, . . . just the 

thing for students to use while studying physical diagnosis and the 
more practical departments of medicine.” 

PRESCRIPTION BOOKS. 

Wythe’s Dose and Symptom Book. Containing the Doses 
and Uses of all the principal Articles of the Materia Medica, etc. 
Seventeenth Edition. Completely Revised and Rewritten. Just 
Ready. 32mo. Cloth, 1.00; Pocket-book style, 1.25 

Pereira’s Physician’s Prescription Book. Containing Lists 
of Terms, Phrases, Contractions and Abbreviations used in 
Prescriptions Explanatory Notes, Grammatical Construction ol 
Prescriptions, etc., etc. By Professor Jonathan Pereira, m.d. 
Sixteenth Edition. 32010. Cloth, 1.00; Pocket-book style, 1.2s 

PHARMACY. 

Stewart’s Compend of Pharmacy. Based upon Remington’s 
Text-Book of Pharmacy. Third Edition, Revised. With new 
Tables, Index, Etc. Cloth, 1.00 ; Interleaved for Notes, 1.25 

Robinson. Latin Grammar of Pharmacy and Medicine. 

By H. D. Robinson, ph.d.. Professor of Latin Language and 
Literature, University of Kansas, Lawrence. With an Intro¬ 
duction by L. E. Sayre, ph.g.. Professor of Pharmacy in, and 
Dean of, the Dept, of Pharmacy, University of Kansas. i2mo. 

Cloth, 2.00 

SKIN DISEASES. 

Anderson, (McCall) Skin Diseases. A complete Text-Book, 
with Colored Plates and numerous Wood Engravings. 8vo. 

Cloth, 4.50; Leather, 5.50 
Van Harlingen on Skin Diseases. A Handbook of the Dis¬ 
eases of the Skin, their Diagnosis and Treatment (arranged alpha¬ 
betically). By Arthur Van Harlingen, m.d., Clinical Lecturer 
on Dermatology, Jefferson Medical College; Prof, of Diseases of 
the Skin in the Philadelphia Polyclinic. 2d Edition. Enlarged. 
With colored and other plates and illustrations. i2mo. Cloth, 2.50 
See pages 2 to 5 for list of New Manuals. 



STUDENTS’ TEXT-BOOKS AND MANUALS. 13 


SURGERY AND BANDAGING. 

Moullin’s Surgery, A new Text-Book. 500 Illustrations, 200 of 
which are original. Cloth, 7.00; Leather, 8.00 

Jacobson. Operations in Surgery. A Systematic Handbook 
for Physicians, Students and Hospital Surgeons. By W. H. A. 
Jacobson, b a., Oxon. f.r.c.s. Eng.; Ass’t Surgeon Guy’s Hos¬ 
pital ; Surgeon at Royal Hospital for Children and Women, etc. 
199 Illustrations. 1006 pages. 8vo. Cloth. 5.00; Leather, 6.00 

Heath’s Minor Surgery, and Bandaging. Ninth Edition. 142 
Illustrations. 60 Formulae and Diet Lists. Cloth, 2.00 

Horwitz’s Compend of Surgery, Minor Surgery and 
Bandaging, Amputations, Fractures, Dislocations, Surgical 
Diseases, and the Latest Antiseptic Rules, etc., with Differential 
Diagnosis and Treatment. By Orville Horwitz, b.s., m.d.. 
Demonstrator of Surgery, Jefferson Medical College. 4th edition. 
Enlarged and Rearranged. 136 Illustrations and 84 Formulae. 
i2mo. Cloth, 1.00; Interleaved for the addition of Notes, 1.25 

*** The new Section on Bandaging and Surgical Dressings, con¬ 
sists of 32 Pages and 41 Illustrations. Every Bandage of any 

importance is figured. This, with the Section on Ligation of 

Arteries, forms an ample Text-book for the Surgical Laboratory. 

Walsham. Manual of Practical Surgery. For Students and 
Physicians. By Wm. J. Walsham, m.d., f.r.c.s.. Asst. Surg. 
to, and Dem. of Practical Surg. in, St. Bartholomew’s Hospital, 
Surgeon to Metropolitan Free Hospital, London. With 236 
Engravings. See Page 2. Cloth, 3.00; Leather, 3.50 

URINE, URINARY ORGANS, ETC. 

Holland. The Urine, and Common Poisons and The 
Milk. Chemical and Microscopical, for Laboratory Use. Illus¬ 
trated. Fourth Edition. i2mo. Interleaved. Cloth, 1.00 

Ralfe. Kidney Diseases and Urinary Derangements. 42 Illus¬ 
trations. i2mo. 572 pages. Cloth, 2.75 

Marshall and Smith. On the Urine. The Chemical Analysis of 
the Urine. By John Marshall, m.d., Chemical Laboratory, Univ. 
of Penna; and Prof. E. F. Smith, ph.d. Col. Plates. Cloth, 1.00 

Tyson. On the Urine. A Practical Guide to the Examination 
of Urine. With Colored Plates and Wood Engravings. 7th Ed. 
Enlarged. i2mo. Cloth, 1.50 

Van Niiys, Urine Analysis. Illus. Cloth, 2.00 

VENEREAL DISEASES. 

Hill and Cooper. Student’s Manual of Venereal Diseases, 
with Formulae. Fourth Edition. i2mo. Cloth, 1.00 

gcjT See pages 14 and 15 for list of * Qutz-Compends f 



NEW AND REVISED EDITIONS. 

?QUIZ-COMPENDS? 

The Best Compends for Students’ Use 
in the Quiz Class, and when Pre¬ 
paring for Examinations. 

Compiled in accordance with the latest teachings of promi¬ 
nent lecturers and the most popular Text-books. 

They form a most complete, practical and exhaustive 
set of manuals, containing information nowhere else col¬ 
lected in such a condensed, practical shape. Thoroughly 
up to the times in every respect, containing many new 
prescriptions and formulae, and over two hundred and 
fifty illustrations, many of which have been drawn and 
engraved specially for this series. The authors have had 
large experience as quiz-masters and attaches of colleges, 
with exceptional opportunities for noting the most recent 
advances and methods. 

Cloth, each $1.00. Interleaved for Notes, $1.25. 

No. 1. HUMAN ANATOMY, “ Based upon Gray.” Fifth 
Enlarged Edition, including Visceral Anatomy, formerly 
published separately. 16 Lithograph Plates, New 
Tables and 117 other Illustrations. By Samuel O. L. 
Potter, m.a., m.d., m.r.c.p. (Lond.,) late A. A. Surgeon U. S. 
Army. Professor of Practice, Cooper Medical College, San Fran¬ 
cisco. 

Nos. 2 and 3. PRACTICE OF MEDICINE. Fourth Edi¬ 
tion. By Daniel E. Hughes, m.d., Demonstrator of Clinical 
Medicine in Jefferson Medical College, Philadelphia. In two parts. 
Part I.—Continued, Eruptive and Periodical Fevers, Diseases 
of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver, 
Kidneys, etc. (including Tests for Urine), General Diseases, etc. 

Part II.—Diseases of the Respiratory System (including Phy¬ 
sical Diagnosis), Circulatory System and Nervous System; Dis¬ 
eases of the Blood, etc. 

*** These little books can be regarded as a full set of notes upon 
the Practice of Medicine, containing the Synonyms, Definitions, 
Causes, Symptoms, Prognosis, Diagnosis, Treatment, etc., of each 
disease, and including a number of prescriptions hitherto unpub¬ 
lished. 

No. 4. PHYSIOLOGY, including Embryology. Sixth 
Edition. By Albert P. Brubaker, m.d., Prof, of Physiology, 
Penn’a College of Dental Surgery; Demonstrator of Physiology 
in Jefferson Medical College, Philadelphia. Revised, Enlarged, 
with new Illustrations. 

No. 5. OBSTETRICS. Illustrated. Fourth Edition. By 

Henry G. Landis, m.d., Prof, of Obstetrics and Diseases of 
Women, in Starling Medical College, Columbus, O. Revised 
Edition. New Illustrations. 


BLAKISTON’S ? QUIZ-COMPENDS ? 

No. 6. MATERIA MEDICA, THERAPEUTICS AND 
PRESCRIPTION WRITING. Fifth Revised Edition. 

With especial Reference to the Physiological Action of Drugs, 
and a complete article on Prescription Writing. .Based on the 
Last Revision of the U. S. Pharmacopoeia, and including many 
unofficinal remedies. By Samuel O. L. Potter, m.a., m.d., 
m.r.c.p. (Lond.,) late A. A. Surg. U. S. Army; Prof, of Practice, 
Cooper Medical College, San Francisco. Improved and Enlarged, 
with Index. 

No. 7. GYNAECOLOGY. A Compend of Diseases of Women. 
By Henry Morris, m.d.. Demonstrator of Obstetrics, Jefferson 
Medical College, Philadelphia. 45 Illustrations. 

No. 8. DISEASES OF THE EYE AND REFRACTION, 
including Treatment and Surgery. By L. Webster Fox, m.d., 
Chief Clinical Assistant Ophthalmological Dept., Jefferson Med¬ 
ical College, etc., and Geo. M. Gould, m.d. 71 Illustrations, 39 
Formulae. Second Enlarged and Improved Edition. Index. 

No. 9. SURGERY, Minor Surgery and Bandaging. Illus¬ 
trated. Fourth Edition. Including Fractures, Wounds, 
Dislocations, Sprains, Amputations and other operations; Inflam¬ 
mation, Suppuration, Ulcers, Syphilis, Tumors, Shock, etc. 
Diseases of the Spine, Ear, Bladder, Testicles, Anus, and 
other Surgical Diseases. By Orville Horwitz, a.m., m.d., 
Demonstrator of Surgery, Jefferson Medical College. Revised 
and Enlarged. 84 Formulae and 136 Illustrations. 

No. 10. CHEMISTRY. Inorganic and Organic. For Medical 
and Dental Students. Including Urinary Analysis and Medical 
Chemistry. By Henry Lf.ffmann, m.d.. Prof, of Chemistry in 
Penn'a College of Dental Surgery, Phila. Third Edition, Revised 
and Rewritten, with Index. 

No. 11. PHARMACY. Based upon “ Remington’s Text-book 
of Pharmacy.” By F. E. Stewart, m.d., ph.g., Quiz-Master 
at Philadelphia College of Pharmacy. Third Edition, Revised. 
No. 12. VETERINARY ANATOMY AND PHYSIOL¬ 
OGY. 29 Illustrations. By Wm. R. Ballou, m.d., Prof, of 
Equine Anatomy at N. Y. College of Veterinary Surgeons. 

No. 13. DENTAL PATHOLOGY AND DENTAL MEDI¬ 
CINE. Containing all the most noteworthy points of interest 
to the Dental student. By Geo. W. Warren, d.d.s., Clinical 
Chief, Penn’a College of Dental Surgery, Philadelphia. Ulus. 
No. 14. DISEASES OF CHILDREN. By Dr. Marcus P. 
Hatfield, Prof, of Diseases of Children, Chicago Medical 
College. Colored Plate. 

Bound in Cloth, $1. Interleaved, for the Addition of Notes, $1.25. 

These books are constantly revised to keep tcp with 
the latest teachings and discoveries > so that they contain 
all the new methods arid principles. No series of books 
are so complete in detail , concise in language, or so well 
printed and bound. Each one fonns a complete set of 
notes upon the subject under consideration. 

Illustrated Descriptive Circular Free. 


JUST PUBLISHED. 


GOULD’S NEW 

Medical Dictionary 



It contains Tables of the Arteries, Bacilli, Gan¬ 
glia, Leucomaines, Micrococci, Muscles, 
Nerves, Plexuses, Ptomaines, etc., 
etc., that will be found of great 
use to the student. 


Small octavo, 520 pages, Half-Dark Leather, . $3.25 

With Thumb Index, Half Morocco, marbled edges, 4.25 


From J. M. DaCOSTA, M. D., Professor of Practice and 
Clinical Medicine, Jefferson Medical College, Philadelphia. 

“Ifind it an excellent work, doing credit to the learning and 
discrimination of the author.” 


c * Sample Pages free, 












A UNIQUE BOOK. 


POTTER’S MATERIA MEDICA, PHARMACY AND THERA¬ 
PEUTICS. Second Edition. Revised and Enlarged. A Hand¬ 
book; including the Physiological Action of Drugs, Special Therapeutics 
of Diseases, Official and Extemporaneous Pharmacy, etc. By S. O. L. 
Potter, m.a., m.d., Professor of the Practice of Medicine in Cooper 
Medical College, San Francisco; Late A. A. Surgeon, U. S. Army, etc. 
A new Edition in larger type. Octavo. Cloth, $4.00; Leather, $5.00. 

Dr. Potter has become well known as an able compiler, by his Compends 
of Anatomy, and of Materia Medica, both of which have reached four editions. 
In this book, more elaborate in its design, he has shown his literary abilities to 
much better advantage, and all who examine or use it will agree that he has 
produced a work containing more correct information in a practical, concise 
form than any other publication of the kind. The plan of the work is new, 
and its contents have been combined and arranged in such a way that it offers 
a compact statement of the subject in hand. 

Part I.— Materia Medica and Therapeutics, the drugs being arranged 
in alphabetical order, with the synonym of each first; then the description of 
the plant, its preparations, physiological action, and lastly its Therapeutics. 
This part is preceded by a section on the classification of medicines as follows: 
Agents acting on the Nervous System, Organs of Sense, Respiration, Circu¬ 
lation, Digestive System, on Metabolism (including Restoratives, Alteratives, 
Astringents, Antipyretics, Antiphlogistics and Antiperiodics, etc.). Agents act¬ 
ing upon Excretion, the Generative System, the Cutaneous Surfaces, Microbes 
and Ferments, and upon each other. 

Part II.— Pharmacy and Prescription Writing. Written for the use 
of physicians who put up their own prescriptions. It includes—Weights and 
Measures, English and the Metric Systems. Specific Gravity and Volume. 
Prescriptions.—Their principles and combinations; proper methods of writing 
them; abbreviations used, etc. Stock solutions and preparations, such as a 
doctor should have to compound his own prescriptions. Incompatibility, 
Pharmaceutical and Therapeutical. Liquid, Solid and Gaseous Extempo¬ 
raneous Prescriptions. 

Part III.— Special Therapeutics, an alphabetical List of Diseases—a 
real Index of Diseases —giving the drugs that have been found serviceable 
in each disease, and the authority recommending the use of each; a very im¬ 
portant feature, as it gives an authoritative character to the book that is unusual 
in works on Therapeutics, and displays an immense amount of research on the 
part of the author. 600 prescriptions are given in this part, many being over 
the names of eminent men. 

The Appendix contains lists of Latin words, phrases and abbreviations, with 
their English equivalents, used in medicine, Genitive Case Endings, etc. 36 
Formulae for Hypodermic Injections; a comparison of 10 Formulae of Chloro- 
dyne; Formulae of prominent patent medicines; Poisons and their Antidotes; 
Differential Diagnosis; Notes on Temperature in Disease; Obstetrical Memo¬ 
randa; Clinical Examination of Urine; Medical Ethics; Table of Specific 
Gravities and Volumes; Table showing the number of drops in a fluidrachm 
of various liquids and the weight of one fluidrachm in grains, and a table for 
converting apothecaries’ weights and measures into grams. 


A MINE OF WEALTH FOR THE STUDENT. 




Standard Text-Books. 

LANDOIS’ HUMAN PHYSIOLOGY. A Text-Book of Human Physi¬ 
ology, including Histology and Microscopical Anatomy, with special 
reference to the requirements of Practical Medicine. By Dr. L. 

Landois, Professor of Physiology and Director of the Physiological Insti¬ 
tute, University of Greifswald. Translated from the Fifth German Edition, 
with additions by Wm. Stirling, m.d., Sc.d., Brackenburg, Professor of 
Physiology and Histology in Owen’s College and Victoria University, Man¬ 
chester ; Examiner in the Honors’ School of Science, University of Ox¬ 
ford, England. Third Edition, revised and enlarged. 692 Illustrations. 
One Volume. Royal Octavo. Cloth, $6.50; Leather, $7.50. 

" With this Text-book at command, no Student could fail in his examination."— 
The Lancet. 

“One of the most practical works on Physiology ever written, forming a ‘bridge* be¬ 
tween Physiology and Practical Medicine. ... Its chief merits are its completeness and 
conciseness. . . . Excellently clear, attractive and succinct.”— British Medical 
Journal. 

“ Unquestionably the most admirable exposition of the relations of Human Physiology to 
Practical Medicine ever laid before English readers.”— Students' Journal. 

“ Landois* Physiology is, without question, the best text-book on the subject that has ever 
been written.”— New York Medical Record. 

CAZEAUX AND TARNIER’S MIDWIFERY. Eighth Revised 
and Enlarged Edition. With Appendix, by Munde. The Theory 
and Practice of Obstetrics; including the Diseases of Pregnancy and 
Parturition, Obstetrical Operations, etc. By P. Cazeaux, Member of 
the Imperial Academy of Medicine. Remodeled and rearranged, with 
revisions and additions, by S. Tarnier, m.d., Prof, of Obstetrics and 
Diseases of Women and Children in the Faculty of Medicine of Paris. 
Eighth American, from the Eighth French and First Italian Editions. 
Edited and Enlarged by Robert J. Hess, m.d., Physician to the Northern 
Dispensary, Phila., etc., with an Appendix by Paul F. Mund£, m.d., 
Professor of Gynaecology at the New York Polyclinic, Vice-President 
American Gynaecological Society, etc. With Chromo-Lithographs, Litho¬ 
graphs, and other Full-page Plates, seven of which are beautifully colored, 
and numerous Wood Engravings. One Volume, octavo. 

Cloth, $5.00; Full Leather, $6.00. 
MEYER ON DISEASES OF THE EYE. A Manual of Ophthal¬ 
mology. By Dr. Edouard Meyer, Prof. & l’ficole Pratique de la Faculty 
M6decine de Paris; Chevalier of the Legion of Honor, etc. Translated 
from the Third French Edition, with the assistance of the author, by Dr. 
Freeland Fergus, Assistant Surgeon, Glasgow Eye Infirmary. With 267 
Illustrations and three Colored Plates. Prepared under the direction of Dr. 
R. Liebreich. 8vo. Cloth, $4.50; Leather, $5.50. 

The first chapter is an explanation of the best means for examining the eyes, 
externally and internally, with a view to diagnosis, the various ophthalmo¬ 
scopes, general considerations on the treatment of ophthalmia, etc. Each dis¬ 
ease is then taken up in its proper order; the anatomy of the part being pre¬ 
sented first, followed by the diagnosis, causes, progress, prognosis, etiology and 
treatment. The arrangement of the work will thus be seen to be systematic, 
commending itself to all physicians and students for the logical and concise 
way in which the facts are given. This English edition makes the eighth 
language into which Meyer’s book has been translated. 


P. BLAKISTON, SON & CO., Publishers and Booksellers, 
1012 WALNUT STREET, PHILADELPHIA 



Standard Text-Books. 

HOLDEN’S ANATOMY. A Manual of the Dissections of the Human 
Body. By Luther Holden, f.r.c.s. Fifth Edition. Carefully Revised 
and Enlarged, specially concerning the Anatomy of the Nervous System 
Organs of Special Sense, etc. By John Langton, f.r.c.s., Surgeon to, 
and Lecturer on Anatomy at, St. Bartholomew’s Hospital. 208 Illustrations. 
8vo. Cloth, $5.00; Leather, $ 6.00. 

Oil-cloth Covers, for the Dissecting Room, $4.50. 

The popularity of this work has steadily increased during the past few years. It is proba¬ 
bly used more extensively than any other dissector. The Oil-cloth binding allows of wash¬ 
ing, and does not retain the dirt and odor of the dissecting table. This edition has been 
carefully printed and bound, and lays open flat at any page. 

“ No student of anatomy can take up this book without being pleased and instructed. Its 
diagrams are original, striking and suggestive, giving more at a glance than pages of text 
description. All this is known to those who are already acquainted with this admirable 
work; but it is simpe justice to its value, as a work for careful study and reference, that 
these points be emphasized to such as are commencing their studies. The text matches the 
illustrations in directness of practical application and clearness of detail.”— New York Med¬ 
ical Record. 

ANDERSON ON SKIN DISEASES. A complete Treatise on Skin 
Diseases. By McCall Anderson, m.d., Professor of Clinical Medicine, 
University of Glasgow. With numerous wood engravings and several col¬ 
ored and steel plates. Octavo. Cloth, #4.50. Leather, $5.50. Just Ready. 

This aims to be a complete text-book. It will be found to contain all the latest methods 
of treatment. The subject is dealt with in a systematic, practical manner, and is based on 
an extensive experience of nearly twenty-five years. 

GOWERS' MANUAL OF DISEASES OF THE NERVOUS 
SYSTEM. A Complete Text-book. By William R. Gowers, m.d., 
Professor Clinical Medicine, University College, London. Physician to 
National Hospital for the Paralyzed and Epileptic. Comprising over 
400 Illustrations and 1360 pages. Octavo. Cloth, $6.50; Leather, $7.50. 

BYFORD. DISEASES OF WOMEN. The Practice of Medicine and 
Surgery, as applied to the Diseases and Accidents Incident to Women. 
By W. H. Byford, a.m., m.d., Professor of Gynaecology in Rush Medical 
College and of Obstetrics in the Woman’s Medical College; Surgeon to 
the Woman’s Hospital; Ex-President American Gynaecological Society, 
etc.; and Henry T. Byford, m.d., Surgeon to the Woman’s Hospital 
of Chicago; Gynaecologist to St. Luke’s Hospital; President Chicago 
Gynaecological Society, etc. Fourth Edition, Revised, Rewritten and 
Enlarged. With 306 Illustrations, over 100 of which are original. Octavo. 
832 pages. Cloth, $5.00; Leather, $6.00. 

" In short, the book is brought up to the standard of to-day, and in most respects may be 
considered a reliable, practical text-book, written by an earnest worker and practical man.” 
—American Journal of Medical Sciences. 

ROBERTS. PRACTICE OF MEDICINE. The Theory and Prac¬ 
tice of Medicine. By Frederick Roberts, m.d., Professor of Thera¬ 
peutics at University College, London. Seventh American Edition, 
thoroughly revised and enlarged, with new Illustrations. 8vo. Cloth, 
$5.50; Leather, $6.50. 

“ If there is a book in the whole of medical literature in which so much is said in so few 
words, it has never come within our reach.”— Chicago Medical Journal. 

“ The best text-book for students. We know of no work in the English language, or of 
any other, which competes with this one.”— Edinburgh Medical Journal. 


P. BLAKISTON, SON & CO., Publishers and Booksellers. 
1912 WALNUT STREET, PHILADELPHIA. 








































